MLB: Why Wins Cannot Be Used Alone When Evaluating a Pitcher’s Season
September 6, 2011 · Harold Friend · Jump to comments
Article Source: Bleacher Report - New York Yankees
It has become almost heresy to still think that a pitcher’s wins are a good measure of a pitcher’s effectiveness. When put in context, wins are a valuable, but they are an extremely limited measurement.
At the close of play on Sept. 5, 2011 there were 12 American League pitchers with at least 13 wins.
The Pearson product-moment correlation coefficient between those 12 pitchers’ wins and ERA+ was calculated.
The result revealed that a positive correlation of 0.70 exists between the two measurements. Simply stated, wins and preventing runs are correlated positively, but not extremely strongly.
A key is that using only wins to evaluate a pitcher does not reveal much, but using wins and ERA, ERA+ and WHIP is an excellent way to determine a pitcher’s effectiveness.
The following table presents the top 12 winning pitchers’ number of wins and their ERA+ in 2011:
PITCHER WINS ERA+
Verlander 21 173
Sabathia 19 146
Weaver 16 153
Nova 15 111
Haren 14 119
Lester 14 138
Shields 14 133
Wilson 14 133
Scherzer 14 94
Holland 13 106
Hernandez 13 118
Romero 13 142
Max Scherzer has won 14 games with an ERA+ that is below the American League’s average, while Derek Holland, with 13 wins, has an ERA+ just above average.
Ivan Nova’s 15 wins are fourth best in the league, yet he has a pedestrian 111 ERA+.
Those who claim that luck, team defense and ball parks affect a pitcher’s wins have a point.
Jusitn Verlander, Jered Weaver and C.C. Sabathia increase the value of the positive correlation, which reveals a weakness in correlating wins with ERA+.
Let’s now calculate the correlation between last year’s top ten American League winning pitchers, which is interesting because the Cy Young Award winner, Felix Hernandez, won only 13 games with an outstanding 175 ERA+.
King Felix led the league with a 2.27 ERA, had a 1.057 WHIP and struck out more than three batters for every walk that he allowed. Still, he had only 13 wins, which was tied for eighteenth in the league. Was Felix Hernandez only the league’s 18th best pitcher?
2010 Top Winners and ERA+
PITCHER WINS ERA+
Sabathia 21 134
Lester 19 133
Price 19 144
Cahill 18 138
Hughes 18 102
Verlander 18 123
Buchholz 17 185
Pavano 17 110
Santana 17 102
Cecil 15 100
The correlation is a mere 0.29, which reveals an extremely low relationship between wins a ERA+
Phil Hughes won 18 games but had an ERA+ of only 102, Carl Pavano won 17 games with a 110 ERA+ and Ervin Santana, like Pavano, won 17 games, but with a 102 ERA+.
The real “villain” was Clay Buchholz, whose 185 ERA+ resulted in 17 wins.
Questions remain because the correlations between wins and ERA, WHIP, batting average against and the ratio of ground outs to fly outs must be calculated.
Evidence strongly indicates that using only wins to evaluate a pitcher is foolish.
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