NBA playoff win probabilities for 2015

nba_playoffs_2015You want to know which team will win the NBA playoffs.

Can Golden State continue their magical season and win the championship? Or will another contender like San Antonio or Cleveland steal the crown?

I had a tough time calculating playoff win probabilities this year because of Cleveland and San Antonio. Both these teams started the season slow.

However, San Antonio has an aging core that won the title last season, and Cleveland has the best player on the planet in LeBron James.

I calculated win probabilities based on my NBA team rankings that take the margin of victory in regular season games and adjust for strength of schedule. It gave Golden State a 56% chance to win the title, which seemed too high.

As an alternative, I estimated the late season form of San Antonio and Cleveland through the betting markets. I took the closing point spread in all games since late February and applied my ranking algorithm to adjust for strength of schedule.

In these market rankings, Golden State is still the best team. However, their rating is only about one point better than San Antonio and Cleveland. The difference was more than 3 points in my team rankings.

With the market rankings, Golden State has a 39.5% to win the NBA championship. They benefit from a first round matchup between San Antonio and the Los Angeles Clippers, their toughest competition in the West.

To see all of my NBA win probabilities, check out this interactive visual from Andrew Phillips of Chartball. Hover over a team to see its chance to advance through each round. Hover over a circle to find the likelihood that each team wins a round.

This list gives the title chances for all 16 NBA teams in the playoffs.

1. Golden State, 39.5%.
2. Cleveland, 26.8%.
3. San Antonio, 14.3%.
4. Atlanta, 5.2%.
5. Los Angeles Clippers, 5.1%.
6. Houston, 2.8%.
7. Memphis, 1.7%.
8. Chicago, 1.2%.
9. Toronto, 1.0%.
10. Portland, 0.8%.
11. Washington, 0.7%.
12. Dallas, 0.5%.
13. Boston, 0.1%.
14. New Orleans, 0.1%.
15. Milwaukee, 0.1%.
16. Brooklyn, 0.1%.

I will update the interactive visual the morning after each day of games, so check back for the latest win probabilities.

The Power Rank best at predicting the 2015 NCAA tournament

Screen Shot 2015-04-13 at 12.26.06 PMYou have a lot of choices for predicting the NCAA tournament.

My probability for each team to advance through each round appear in this interactive visual. However, these other quants perform the same calculation.

Which tournament win probabilities were the most accurate in 2015?

Reuben Fisher-Baum of FiveThirtyEight took a quantitative approach to determining which tournament predictions were most accurate. He looked at how a predicted probability deviated from the actual result in the tournament.

For example, my numbers gave a 70.7% chance for Duke to advance to the Elite 8. Since Duke did advance to that round, we assign that result the number 1.0. The square of the deviation, or (1.0 – 0.707) squared, gives a Brier score for that prediction. For an event that happened, a larger probability is better, so a lower Brier score implies a better prediction.

From FiveThirtyEight’s analysis, The Power Rank had the most accurate 2015 tournament predictions.


Duke’s run through the tournament helped out my method rise to the top. Of all the models, my numbers had the highest probability for Duke to advance to the Sweet 16 and every round after that.

FiveThirtyEight gave this very kind conclusion.

Given that Duke is traditionally undervalued in bracket pools, fans who built their brackets on The Power Rank’s numbers likely had a pretty good tournament.

Indeed, some people did have such success.

Ryan Peters bought my book on how to win your pool and knew the importance of picking a value champion, or a team with a high win probability overlooked by others in his pool. He chose Duke and sent this tweet on the eve of the championship game.

I had Duke ranked third in my team rankings heading into the tournament. They got credit for playing a tough ACC schedule which included Virginia, Notre Dame (3 times), North Carolina (twice) and Louisville, all top 20 teams in The Power Rank. These strength of schedule adjustments moved Duke higher compared to other rankings.

The Power Rank came out on top this year, but don’t expect these results every year against stiff competition. One tournament represents a small sample size of 67 games. Had Kentucky won the tournament like my numbers expected (38% win probability), the results could have been different.

Can Justin Verlander stay healthy in 2015?

Screen Shot 2015-04-07 at 7.07.07 AMJustin Verlander is a huge question mark for the Detroit Tigers. The former Cy Young winner has a triceps strain in his pitching arm and won’t make his first start until April 12 at the earliest.

Will this injury derail his season? Or is this injury a fluke that will seem like a distant memory when Verlander throws his 200th inning in September?

In my latest column for the Detroit News, I use the injury analytics of Jeff Zimmerman of Fangraphs to analyze Verlander’s situation. I also look at the other starters for the Tigers.

To read the column, click here.

John Calipari is a better tournament coach than Tom Izzo

calipariJohn Calipari evokes many different emotions in sports fans.

If you’re a Kentucky fan, you probably love Calipari. In six years as coach, he has won a national championship, and his 2015 team might win another with an undefeated record.

If you’re not a Kentucky fan, Calipari represents all that’s wrong with college basketball. His teams at Massachusetts and Memphis had to vacate wins during Final Four years because of NCAA rules violations. While the NCAA never found Calipari guilty of anything, it seems unlikely he knew nothing about the infractions.

Moreover, Calipari pisses off his colleagues. At a press conference, he got former Temple coach John Chaney so mad that Chaney attacked him, yelling “I’ll kill you.” Yes, this really happened; check out the video.

Numbers reveal a third side Calipari: he’s an amazing tournament coach. This article looks at how teams perform in the tournament compared with a regular season baseline. With a high degree of statistical certainty, Calipari’s teams play better in March than the regular season.

Calipari’s ability to get more out of his teams during the tournament is neither a typical part of his narrative nor the story in which I was originally interested. Michigan State coach Tom Izzo usually gets praised for his excellent coaching in March. I didn’t believe this conventional wisdom, so I dug into the numbers.

Comparing tournament performance with the regular season

To test Michigan State’s play in the tournament, I compared their margin of victory in the post season with expectations from the regular season.

For a regular season baseline, I used my college basketball team rankings at The Power Rank. Developed from my Ph.D. research in statistical physics, this algorithm takes margin of victory and adjusts for strength of schedule.

From 2002 through 2014, the higher ranked team in my pre-tournament rankings won 71.3% of games. In addition, the rankings provide a predicted margin of victory in each game. We’ll use this prediction as a baseline for tournament performance since, unlike the point spread in Vegas, it makes no preference for Michigan State or any other team in March.

For all tournament games from 2012 through 2015, I looked at Michigan State’s actual margin of victory compared with The Power Rank’s prediction. For example, in 2015, Michigan State beat Virginia by 6 points and exceeded the baseline prediction by 12.1 points. In 43 games tournament games, Michigan State has exceeded their expectation from The Power Rank by an average of 2.07 points.

Two points might not seem like a lot, but it’s a huge jump in performance. If the betting markets favor a college basketball team by 2 points, this teams wins the game 58.4% of the time, much more than the 50% for a game with a zero point spread.

Are these results statistically significant?

However, we can’t just assume that Michigan State performs better in the tournament based on this 2.07 points. There’s randomness in this estimate. We don’t know whether Michigan State performed at the same level as the regular season and got lucky by two points a game. Or Michigan State could be 4 points better than the regular season and got unlucky in the tournament.

Statistics gives us tools to account for the randomness in this estimate. A t-test, a method first developed at the Guinness Brewery, provides a probability that this estimate of 2.07 points is better than zero. This test, using this nifty calculator, gives a 92.6% confidence that Michigan State performs better in the tournament. (For those who want to check my work, the standard deviation of sample mean over 43 games was 1.40 points.)

I was wrong. The numbers suggests a high likelihood that Tom Izzo’s teams perform better in the tournament. Conventional wisdom wins this time.

The greatness of John Calipari

With the code to perform this test for Tom Izzo, I decided to repeat the test for the other Final Four coaches in 2015.

Duke coach Mike Krzyzewski has a reputation for getting the most of his players in March. However, since 2002, they have performed 0.41 points worse than The Power Rank’s expectation from the regular season.

Wisconsin coach Bo Ryan did slightly better than Krzyzewski in the tournament. However, his teams still performed 0.21 points worse than expected over 37 games.

John Calipari was a different story. During his years at Kentucky (2010 to present), his teams have performed 3.86 points better than their regular season expectation. Even with the smaller sample size than the other coaches (25 games), we can be 98.1% sure Kentucky has played better in the tournament.

Calipari also coached at Memphis before taking the Kentucky job. From 2002 through 2009, his Memphis teams exceeded their regular season expectation by 1.38 points in 20 tournament games.

It’s probably best to combine the tournament performances of Calipari’s Kentucky and Memphis teams, which gives a 2.76 point improvement over 45 games. That implies a 96.8% confidence that his teams play better in the tournament. In addition, Calipari’s tournament improvement is 35% larger than Tom Izzo’s improvement.

The following list summarizes the difference in tournament performance from the regular season since 2002.

  • John Calipari: + 2.76 points per game.
  • Tom Izzo: +2.04 points per game.
  • Bo Ryan: -0.21 points per game.
  • Mike Krzyzewski: -0.41 points per game.

For the 2015 Final Four, the main story should be John Calipari’s greatness as a tournament coach.

The top 10 college basketball teams in 2015 by Sweet 16 appearances

tom_izzoWhich school has the best college basketball program?

It’s an easy question to answer with only analytics. We could take an average rating from computer rankings over the past 10 years to find the best programs.

However, college basketball is a sport that almost entirely relies on the postseason for its popularity. Any legitimate ranking must consider success in the NCAA tournament.

To balance analytics with post season success, I propose ranking programs by Sweet 16 appearances over the past 10 years. With such a long time period, it’s difficult for a non-elite team by the numbers to have enough tournament success to make this list. The top 10 below includes all the traditional college basketball powers.

In addition, the Sweet 16 seems like an appropriate balance between making the tournament and winning the entire contest. It’s not enough to just make the field every year, but there’s too much randomness in winning the tourney. In the past 10 years, only two programs have won more than one tournament (Florida and Connecticut), and neither made the tournament in 2015.

To break ties among programs with the same number of Sweet 16 appearances over the last 10 years, I looked at appearances in the past 9 seasons. If this didn’t break the tie, I looked at successively shorter time periods until one program came out ahead.

The rankings below show the top 10 college basketball programs by Sweet 16 appearances. Only one program had 7 appearances over 10 years, which shows the parity in college basketball. Even the best programs have years in which they lose before the second weekend of the tournament.

Teams that missed the cut

Gonzaga has made the tournament each of the past 10 years but did not make this list. While they have become a brand name program in college basketball, Gonzaga has struggled in the tournament with only 3 Sweet 16 appearances.

Ohio State and UCLA have 5 Sweet 16 appearances each but lost out to the teams below based on the tie breaker method. Ohio State hasn’t make the second weekend of the tournament the last two years, while UCLA had 3 straight appearances early in the 10 year window.

10. Xavier

5 Sweet 16’s: 2015, 2012, 2010, 2009, 2008

Xavier is the only program in the top 10 not from a power conference. Sean Miller led the Musketeers to the first two Sweet 16 appearances, while Chris Mack has reached the Sweet 16 in half of his 6 seasons.

9. Wisconsin

5 Sweet 16’s: 2015, 2014, 2012, 2011, 2008

Bo Ryan has made the NCAA tournament in each of his 14 years as Wisconsin’s coach. They have made the Sweet 16 in half of the past 10 years, and the 2015 team led by Frank Kaminsky might be the best of all these teams.

8. Arizona

5 Sweet 16’s: 2015, 2014, 2013, 2011, 2009

Sean Miller coached Arizona for the last 4 Sweet 16 appearances. However, Arizona only had 1 appearance between 2006 and 2010 as the program transitioned from long time coach Lute Olsen to Miller.

Arizona has a great team in 2015, and I think they have the best chance of beating Kentucky should they play in the Final Four.

7. Kentucky

5 Sweet 16’s: 2015, 2014, 2012, 2011, 2010

With their undefeated season so far in 2014-2015, one might expect Kentucky to be higher on this list. However, the Wildcats struggled in the early years of this 10 year period as they transitioned from Tubby Smith to Billy Gillispie (whoa, remember him?) to John Calipari.

Even within the last 5 years, Kentucky had a down year in 2013 when they lost to Robert Morris in the first round of the NIT. Even the best programs can’t escape the vagaries of luck in this era of one and done players.

6. Florida

6 Sweet 16’s: 2014, 2013, 2012, 2011, 2007, 2006

Billy Donovan has had tremendous success at Florida, winning back to back championships in 2006 and 2007. However, it doesn’t always run smoothly in Gainesville. Florida didn’t make the tournament in 2008 and 2009 when the stars from the championship teams left. They also didn’t make the tournament this year.

5. Duke

6 Sweet 16’s: 2015, 2013, 2011, 2010, 2009, 2006

Back in the Christian Laettner years, Duke made four straight Final Four appearances and won two championships. Even Mike Krzyzewski can’t duplicate that success in this era of parity and one and done players.

Duke has fallen victim to two of the biggest Round of 64 upsets recently, as they lost to 15 seed Lehigh in 2012 and 14 seed Mercer in 2014.

4. Kansas

6 Sweet 16’s: 2013, 2012, 2011, 2009, 2008, 2007

Bill Self has an incredible streak of 11 straight Big 12 regular season championships. He also hasn’t made the Sweet 16 the past two seasons. In 2015, Kansas lost Wichita State, a program in their own state they refuse to schedule during the regular season.

3. North Carolina

6 Sweet 16’s: 2015, 2012, 2011, 2009, 2008, 2007

I thought North Carolina would be lower on this list, as Roy Williams has had some subpar teams in recent memory. North Carolina didn’t make the tournament in 2010, and they didn’t make the Sweet 16 in 2013 and 2014. However, they still have 6 appearances over the last 10 years and squeak ahead of Kansas with their Sweet 16 appearance in 2015.

2. Louisville

6 Sweet 16’s: 2015, 2014, 2013, 2012, 2009, 2008

Rick Pitino has the Louisville program in great shape, as they almost always feature a top 10 defense by adjusted points per possession. However, their offense has been the problem in 2015. If they can find enough offense in the soft East Region this year, they could make another Final Four appearance.

1. Michigan State

7 Sweet 16’s: 2015, 2014, 2013, 2012, 2010, 2009, 2008

Tom Izzo’s teams continue to perform well in March. In 2015, Michigan State beat Virginia to make the Sweet 16 for the 7th time over the last 10 years, tops in the country. I doubt Michigan State would have the highest rating averaged over the past 10 seasons, but they continue to have success in the tournament.