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The Best Ace So Far? A Look at mERA

Last year, in response to Kyle Kendrick pitching like a modern day Jeckyll and Hyde, I developed the kERA stat - the ERA difference between a starting pitcher's best and worst starts.

This year, so far at least, in trying to determine which ace has pitched the best, we might have to look at a different form of modified ERA - the mERA.  Let me explain.

Through the Phillies' first 28 games, the four aces have the following lines:

Halladay 46.3 9.1 1.4 7.6 0.2 0.99 1.73 2.14
Hamels 40.7 8.9 2.2 6.9 0.4 1.01 2.45 2.66
Oswalt 27.0 7.0 2.3 7.0 0.7 1.04 3.26 3.33
Lee 39.3 10.1 1.4 8.7 0.9 1.12 2.66 3.66

As Rob Neyer wrote earlier this week, Roy Halladay is the king here -- not only of the Phillies' aces, but of all of baseball.

But what if we look at the Phillies' starters in a slightly different way.  Each starter has had one awful game so far:

  • On April 19, against the Brewers, Halladay gave up 6 earned runs, 10 hits, and 2 walks in 6.67 innings.
  • On April 5, against the Mets, Hamels lasted only 2.67 innings, giving up 6 earned runs on 7 hits and 2 walks.
  • On April 26, against the D-Backs, Oswalt gave up 5 earned runs in 3 innings, allowing 6 hits and 1 walk.
  • On April 8, against the Braves, Lee gave up 6 earned runs in 3.3 innings, allowing 10 hits and 1 walk.

Everyone, even the Phillies' aces, is mortal.  So what if we remove these mulligans from their stats?  How would they look then?  Here's a chart of each pitcher's stats without that one awful game.  They're ranked by mERA (mulligan ERA) but each of their other stats is also mulligan-ed.

mIP mK/9 mBB/9 mH/9 mHR/9 mWHIP mFIP mERA
Halladay 39.7 10.0 1.1 6.6 0.0 0.86 1.44 1.13
Hamels 38.0 8.8 1.9 5.7 0.5 0.84 2.49 1.42
Oswalt 24.0 7.9 2.3 5.6 0.8 0.88 3.41 1.88
Lee 36.0 10.3 1.3 7.0 1.0 0.92 2.87 2.50

As we can see by this chart, Halladay remains king, but the difference between him and the others shrinks.  Although Halladay still has a remarkable advantage over the others in FIP, Hamels and Oswalt join Halladay in having mERAs under 2.  And all of the aces have been incredibly effective in keeping runners off the basepaths, but Hamels has been the best, with an mWHIP of 0.84.  His 2 home runs compared to Halladay's 0 in his non-mulligan games is the big difference in their FIPs.

Basically, without any modification, the Phillies aces have pitched spectacularly.  But, with a slight modification to account for human fallibility, we can see that the Phillies aces have been even better than their raw stats indicate.  Halladay is still the best, but the others are closer behind than you might otherwise think.