The rankings below (2014 season) are based on the Base Runs formula of Dave Smith, basic events version. Over a MLB season, this runs created formula predicts a team’s runs scored and allowed within 1%.
Moreover, the deviation in Base Runs from actual runs is weakly correlated from season to season. Hence, deviations are mostly due to luck.
For each team, the rating plotted along the line is the difference in runs scored and allowed by Smyth’s Base Runs. The Pythagorean expectation turns these numbers into a record for each team (exponent of 1.83).
For more on run creation formulas, check out this article.