Tiger ERA Analysis

Earlier in the week, I spent some time evaluating Tiger batters using the statistic “runs created”. Now I’ll take a look at the pitchers. One of the better statistics for evaluating overall pitching performance is ERA+. ERA+ is more useful than ERA for comparing pitchers pitching in different environments whether it be leagues, ballparks or years ERA+ is a pitcher’s ERA relative to the league average ERA. It is also adjusted for the impact of the pitcher’s home park. A league average ERA+ is 100. An ERA+ of 105 would indicate that the pitcher had an ERA 5% above the league average. Similarly, an ERA+ of 94 means that the pitcher was 6% below the league average.

A pitcher pitching his home games in a pitcher friendly park will have his ERA+ adjusted downward and a pitcher pitching in a hitter friendly park will have his ERA+ adjusted upward. So if two pitchers have the same ERA but one of them pitches for the Dodgers and the other pitchers for the Rockies, the Rockie pitcher will have a higher ERA+. Ballpark factors are very complex and I’ll probably discuss them further in a future post but for now I’ll just point you toward US Patriot if you want a detailed explanation.

It’s important to note that the league average of 100 includes a whole bunch of pitchers who pitched poorly in a few games. So, I threw out all of the pitchers with fewer than 25 innings pitched. Also keep in mind that reliever ERA+’s are inflated because relievers often give up other people’s runs.

Because of the issues discussed above, I took all of the pitchers in the American League in 2005 with 25 or more innings pitched and divided them into primary starters and primary relievers. The median ERA+ for the starters was 106 and the median ERA+ for the relievers was 120.

The tables below give the ERA+ figures for Detroit Tiger pitchers in 2005. The raw data were extracted from statistical tables at The Hardball Times.

Starters

Pitcher	IP	ERA	ERA+
AL Median	***	***	106
Johnson	210	4.54	102
Maroth	209	4.74	98
Robertson	196.7	4.48	103
Bonderman	189	4.57	102
Douglass	87.3	5.56	83
Ledezma	49.7	7.07	66

Relievers

Pitcher	IP	ERA	ERA+
AL Median	***	***	120
Spurling	70.7	3.44	135
German	59	3.66	127
Walker	48.7	3.7	125
Rodney	44	2.86	162
Farnsworth	42.7	2.32	200
Ginter	35	6.17	75
Dingman	32	3.66	127
Urbina	27.3	2.63	176
Percival	25	5.76	81
Colon	25	6.12	76

The four most frequently used starting pitchers – Jason Johnson (102), Mike Maroth (98), Nate Robertson (103) and Jeremy Bonderman (102) were all slightly below the league median for primary starters. The fifth Starters – Sean Douglass (83) and Wil Ledezma (66) were very far below the league median. Douglass is no longer with the organization and Johnson will be a free agent this off-season. It’s no secret that they will be looking to bolster their pitching staff during the winter.

Most of their most frequently used relievers – Chris Spurling (135), Franklin German (127), Jamie Walker (125), Fernando Rodney (162), Kyle Farnsworth (200) and Craig Dingman (127) were above the league median. Barring trades, all of them except Farnsworth (who was traded during the season) should be returning next year. Of course, ERA+,s, just like ERAs, are kind of tricky for relievers but these figures are still encouraging.