Astros' ace Dallas Keuchel pitched in the wild card game with short rest. He was pitching on three days rest for the first time in his career. This was supposed to be a handicap. But it didn't prevent Keuchel from dominating the Yankee's No. 2 ranked offense. Keuchel's tossed shut out ball, allowing only three singles and 1 walk in six innings. That's a zero ERA and a 1.31 Fielding Independent Pitching (FIP). Based on game score, Keuchel was the fourth best short-rest post season pitcher in major league history.
Prior to Tuesday's wild card game, Fangraphs pointed out that the post season ERA for pitchers on short rest is much higher than for pitchers on normal rest. So, I can't blame any Astros' fans who were worried that Keuchel might falter doing something he had never done on short rest. What went right?
In my starting nine comment before Tuesday's game, I suggested that Keuchel wouldn't be hurt by the short rest because he is an extreme ground ball pitcher. Admittedly, this comment was mostly based on optimism. It's an old baseball adage that sinker ball pitchers are better on short rest. But I have not seen any studies which attempt to compare short rest pitching performances based on pitch type.
The notion behind this adage is that a sinker ball pitcher with an arm that isn't at top strength is less likely to overthrow and elevate his pitches. Moreover, a slightly lower velocity may improve the sink on the pitch. It's also possible that a downtick in the velocity will improve command of the four seam fastball. Confirming this notion, in Tuesday's wild card game, Keuchel's 4 seam fastball was a few ticks below his average, and his 2 seam fastball was almost 1 mph below his season average (courtesy of Texasleaguers.com pitch f/x data base.)
Keuchel's opinion is consistent with this traditional view. After the game, Keuchel said he has the style of pitching which benefits from short rest. Not surprisingly, Keuchel was amped up in the first inning with some negative (though harmless) effect on his command. But thereafter, he settled in, with 55% of the at bats against him ending in either a strike out or groundball out.
Looking over the lists of pitchers who have been successful in short rest starting performances in the playoffs, ground ball pitchers seem to have a disproportionate number of performances. This mlb.com article identifies the short rest starters in the post season since 2004 who have pitched more than six innings: Kuroda (2012), Lowe(2010), Sabbathia (twice-2009), and Hudson (2005). All of these pitchers are well known sinker/groundball pitchers.
Extreme ground ball pitchers have displayed some of the most famous short rest performance. Lowe pitched on 2 days rest in the game 7 ALCS comeback over the Yankees, catapulting the Red Sox into the World Series with six innings of 1 run ball. Astros' fans unfortunately remember Kevin Brown and his power sinker defeating the Astros in 1998 on 3 days rest. Chris Carpenter, another groundball pitcher, clinched the Cardinals' 2011 World Series on short rest.
The ESPN broadcasters compared Keuchel to Andy Pettitte's style of pitching. It's not a bad comparison because both are sinker/cutter/slider left handers who rely on painting the strike zone. And Pettitte may be the best and most prolific short-rest post season pitcher in ML history. He has a 3.07 ERA on short rest in six post season games, including pitching on short rest multiple times during a series.
This is all anecdotal evidence and doesn't prove that sinker ball pitchers may benefit from short rest. But it certainly doesn't hurt the traditional view on the subject.
Although it appeared that Keuchel could have pitched another inning or so, A.J. Hinch made the right choice to remove Keuchel after 6 innings. That's what we know in hindsight, but I'm sure that many fans were worried at the time when Hinch went to the bullpen in the 7th inning. This mlb.com article provides support for Hinch's decision:
...history suggests that even pitchers who have had impressive outings on short rest have rarely maintained it for more than six innings.
Give Hinch credit for avoiding any deterioration in Keuchel's performance, while also letting Keuchel miss the 100 pitch mark, which may help him pitch longer in the ALDS.