Zach Greinke's Enigmatic Season

Peter wrote earlier today about one of the biggest acquisitions this past offseason in Jayson Werth, but another, Zach Greinke, has had an equally bizarre season. After starting the season on the disabled list, Greinke has a K% (strikeouts/total batters faced) of 30.9% (the highest among any starter in the majors this season) with a low BB% (walks/total batters faced) of 5.2%. His ground ball/fly ball ratio of 1.29 is the highest of his career. These are the peripherals the Brewers expected when they traded for him to be the ace of their rotation who would lead them to the playoffs. But there is one problem: Greinke currently has a 5.04 ERA.

So what is going on? One problem for Greinke is his 15.3% home run to fly ball ratio (HR/FB), which is roughly twice the rate of last season. Furthermore, hitters have a BABIP (batting average on balls in play) of .343 against him and his left on base percentage (LOB%) of 55.9% is easily the lowest of his career and ninth worst this season by any major league starter. While a lot of this can probably be attributed to poor luck (pitchers often see their BABIP fluctuate wildly from season to season), one cannot automatically assume that Greinke’s numbers will improve due to regression to the mean to some of his uglier numbers. First, his unflattering statistics might not regress back to the mean this season, just as in his stellar 2008 season when his HR/FB ratio ended at 4.5%. Furthermore, even if his HR/FB, BABIP, and LOB% all improve, it is possible that his K% and BB% will also drop the rest of the season, negating some to all of the previous effects. It will also not help his cause that the Brewers are not a good defensive team. This can be seen by advanced defensive statistics (-1.9 UZR/150, -2 DRS) or by the eye test (watching Prince Fielder, Ryan Braun, Yuniesky Betancourt, and Casey McGehee field is not fun for fans of defense). There is also the possibility that he is having some sort of issue while in the stretch which makes it more difficult for him to escape jams, allowing for more runs to be scored against him than expected (although that is strictly conjecture and I have no proof to support this).

When weighing everything, it is still remarkable that Greinke’s ERA is 5.04 ERA. His FIP (fielding independent pitching) of 2.86, xFIP (expected fielding independent pitching) of 2.13 and SIERA (skill independent earned run average) of 2.17 all indicate that Greinke’s results are way out of line with what could be expected. Even his tERA, an ERA estimator that involves all batted ball types, comes out at 3.50, still a run and a half lower than his ERA. So how do you value Greinke’s season so far? Fangraphs, which bases its wins above replacement (WAR) statistic based on FIP, gives Greinke 1.9 WAR this season, tops on the Brewers staff (even though due to injury he has only thrown 80.1 innings) and 45^th among all MLB starters this season. Baseball-Reference’s WAR, however, involves sequencing of events, and therefore runs allowed. Greinke has been worth -.4 WAR this season according to Baseball Reference, meaning the Brewers would have had better results with a pitcher called up from the minors. Fangraphs and Baseball-Reference also disagreed on Greinke’s value last season, as his Fangraphs WAR was more than double of his Baseball-Reference WAR (5.2 vs. 2.3).

Whichever you think is more indicative, the Brewers need better results from Greinke. Among starters with at least 60 innings pitched, Greinke has the highest differential between his ERA and his FIP. Besides his magical 2009 season, he has never had a tERA lower than 3.50 (which it currently is at and was at last year), which is not exactly ace material. For the Brewers to cash in on their gamble to go all-in to make the playoffs this year in a competitive NL Central, Greinke will have to respond like CC Sabathia did for the Brewers three years ago and put up dominant numbers that resonate in the spreadsheets and on the scoreboards.