A Baseball Weblog

Wednesday, June 29, 2011

Putting Greinke's clunker in context

The Yankees knocked around Zack Greinke last night, scoring seven runs against him in only two innings.  Probably the most unusual thing about Greinke's brief (shortest start since 2007) outing was the number of free passes he allowed.  In his 2 innings and 16 batters faced, Greinke allowed three walks and hit a batter - all of this without striking out a single batter.  This coming from a pitcher with a K/BB near 9 coming into yesterday's game.  Strikeouts and free passes are two things that are directly in the pitcher's control, so it's a good (albeit incomplete) thing to look at for evaluating a pitcher's success.  Tom Tango's kwERA (strikeout-walk ERA) is an ERA estimator that only uses strikeouts and free passes (walks - intentional walks + hit batsmen) as inputs and converts the differential into an ERA-like number.  The chart below shows Greinke's kwERA by start, with the horizontal axis being the NL average ERA.

You can see that before yesterday, Greinke hadn't had a worse-than-average game by this measurement all season.  Greinke's still leads his league in kwERA by a lot at 2.12; Clayton Kershaw is next at 2.54.


  1. My understanding is that ZG's performance 'under the spotlight' has been questioned. Is there a way to compare his performances looking at low pressure versus high pressure conditions?

  2. There certainly are; it depends on how you want to define "pressure situation." The way I'd typically think about a pressure situation is within a game; by this definition, a higher-pressure situation indicates one where the game's action most directly affects win expectancy (http://www.hardballtimes.com/main/article/crucial-situations/ is a cool step-by-step way of looking at this). If we define leverage that way, Greinke has a drastic split (2.40 career ERA in 510 "low" leverage innings, 4.37 in 593 2/3 "medium" innings, 11.02 ERA in 72 2/3 "high" innings), though I'd like to see more high leverage innings pitched before saying too much about it. You could also define it as big within a season, which might indicate a playoff game (no playoff games for Greinke yet) or a game in a high-profile city (New York!). Greinke has struggled in New York over 18 1/3 innings (11.29 ERA), but again, I'd feel very uncomfortable using those 18 1/3 innings to make a judgment on Greinke's character. Remember, CC Sabathia also struggled against the Yankees and in the playoffs, and that doesn't seem to mean anything now. It's just very difficult to measure emotional/mental toughness because there are so many other variables (and certainly, a lot of it is random) that affect the outcomes we're looking at.