Wednesday, August 14, 2013

Best Tigers Starting Rotation Since 1940s

Sabertooth, a poster at, remarked recently that the Tigers starting staff has one of the best Adjusted Earned Run Averages (ERA-) in recent years.  Their MLB-leading ERA- of 83 says that their starters have allowed runs at 83% of league average or 17% fewer runs per inning than league average.  This is the 19th best ERA- in MLB (including nine years of the Braves) and 6th best in the AL since 1990.  Upon seeing this, I wanted to see how this years Tigers staff ranked in franchise history.

The ERA- statistic is calculated from team ERA (3.42 for Tigers starters) and league ERA (4.03 overall in the AL for both starters and relievers).  Dividing 3.42  by 4.03 yields 0.85.  Comerica Park inflates ERAs by an estimated 2% so divide by 1.02 to get 0.83.  Finally multiply by 100 to arrive at their 83 ERA-.  An ERA- of 100 is average, below 100 is better than average and above 100 is worse than average.

The ERA- for Tigers starters are as follows:

Anibal Sanchez 63
Max Scherzer 69
Justin Verlander 87
Doug Fister 88
Rick Porcello 107

Sanchez and Scherzer are both in the AL top ten and Verlander and Fister crackthe top twenty.  Porcello's 107 indicates that he has allowed runs at a rate of 7% runs more per inning than league average.  Remember though that the league average also includes relievers.  If we just included starters, he would be just 3% above average which is pretty good for your fifth starter.

The top Adjusted ERAs for Tigers starters since 1901 are listed in Table 1 below.   It shows that the 2013 rotation has the seventh best ERA- in team history.  The top six all occurred in the 1940s with the best one being 76 in 1942. If you eliminate the World War II years of 1943-1945 with their depleted rosters, the 2013 staff ranks fourth.

Table 1: Best Adjusted ERAs for Tigers Since 1901

Data source:

That 1942 staff amazingly had six starters with 20 or more games started all with ERA- of 85 or lower:

Hal Newhouser 63
Tommy Bridges 70
Virgil Trucks 70
Al Benton 75
Hal White 75
Dizzy Trout 85

So, does that make it the best Tigers staff ever? You could make a strong case for it, but ERA- statistic has all the same caveats of ERA in pitcher evaluation.  Most importantly, it assigns all run prevention to pitchers and ignores the contribution of fielders.  Ideally, you want to isolate pitching from defense.

You could use Adjusted FIP (FIP-) which looks only at strikeouts, walks, hits batsmen and home runs.  Based on FIP-, the 2013 Tigers have the second best starting rotation in the history of baseball to the 2011 Phillies!  The FIP stat is good at measuring results on events controlled by the pitcher which is its intended purpose.  However, it ignores the pitcher's responsibility for balls in play which becomes a bigger problem when comparing to eras like the 1940s where there were a lot more balls in play. 

Another possibility is the Baseball-Reference WAR statistic which attempts to remove fielding from run prevention, but that is not split into starters and relievers and defensive metrics are not reliable especially in earlier years.

So for now, I'll just say that the Tigers have their best starting staff in terms of ERA since the 1940's and leave it at that.


  1. Can you solve for what our score would be if we had Verlander's performance from last year as an idea of what it could have been if he was pitching at his best? Just curious what the comparison looks like to then get an idea of how likely it might be for our score to improve next year. Sure we have to get more great performances from the other guys, but Porcello has room to still improve.

  2. Verlander was 63 last year, so the staff would be around 78 this year with the same performance. Like you said though, everybody else has to keep up and pitchers are such unpredictable creatures, you can't be really confident that they'll all repeat. I would guess Sanchez or Scherzer might drop off a bit next year.

    1. Oh ok that's interesting, thanks, just wanted to get an idea for the potential range. I could have said make Porcello have a Verlanderesque score too, but just one big tweak was enough just to help gain some perspective. Also I just wanted to play with the idea of what if the other 4 pitched exactly the same for the rest of the year but Verlander was holding back for some reason on purpose and planning to kick it into high gear for the playoffs. If that was the case then perhaps our playoff group would be around that 78 with all other assumptions naturally having to pan out.


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