Postseason Pitching on Short Days of Rest

Clayton Kershaw shut the door on the Braves in the NLDS by coming back on three days rest, bypassing Ricky Nolasco, who had been 8-3 with a 3.52 ERA and 1.195 WHIP since his acquisition. This is how Kershaw performed:

Year	Series	Date	Tm		Opp	Rslt	Inngs	Dec	DR	IP	H	R	ER	BB	SO	ERA	BF	Pit	Str
2013	NLDS g1	Oct 3	LAD	@	ATL	W,6-1	GS-7	W(1-0)	99	7.0	3	1	1	3	12	1.29	26	124	77
2013	NLDS g4	Oct 7	LAD		ATL	W,4-3	GS-6		3	6.0	3	2	0	1	6	0.69	24	91	61

Provided by Baseball-Reference.com: View Original Table
Generated 10/10/2013.

This got me to thinking about how well pitchers pitch on short days rest and if it's a real phenomenon. Before I dig in, let me make some very important caveats:

1. Days of rest are calculated from GAMES and not dates. Obviously the difference in games was three, but in dates it was four, depending on how the game date is treated. Since Baseball-Reference calculates the data, I'll use their (and the rest of baseball's) definition.

2. I'll use Lance Lynn in 2012 to show another example:

Year	Series	Date	Tm		Opp	Rslt	Inngs	Dec	DR	IP	H	R	ER	BB	SO	ERA	BF	Pit
2012 Postseason	Year	Series	Tm		Opp	Rslt	Inngs	Dec	DR	IP	H	R	ER	BB	SO	ERA	BF	Pit
2012	NLDS g4	Oct 11	STL	@	WSN	L,1-2	9-GF	L(1-1)	2	0.0	1	1	1	0	0	7.36	1	13
2012	NLCS g1	Oct 14	STL	@	SFG	W,6-4	GS-4		2	3.2	5	4	4	2	3	8.59	18	85

Provided by Baseball-Reference.com: View Original Table
Generated 10/10/2013.

If you subscribe to the B-R Play Index feature and enter days of rest of two or fewer for postseason games, Lynn's game of October 14th, 2012 will appear. He DID start on short days of rest, because he had pitched in relief on October 11th. I'm not diminishing his accomplishment, but it's not the same as Kershaw, who started both games. As such, anything I will discuss will be with regard to pitchers that started BOTH games on 3 days of rest. As an aside, Lynn has been in the majors since 2011--and has pitched in 17 postseason games. Since 1980 929 pitchers have pitched in a postseason game--Lynn is already very comfortably in the top 60 or so in appearances among that group.

This chart shows the difference in ERAs for starters on 3 or fewer days of rest compared to those with more since 1980:

These numbers use the shortcomings described in #2 above--many of the games on short days of rest follow a relief appearance. As such, I went through all postseason pitching appearances and did my best to select only those examples such as Kershaw, where one start was followed by another on 3 days of rest. Using this criteria, I found 157 games--this is now how those numbers look:

I left wins out because I didn't calculate them and they weren't my primary measure in the first place for reasons that are well-documented elsewhere. I also include WHIP as a better measure of those factors that are directly in a pitcher's control. Across the board it would appear that there is a decline in performance--the average number of innings pitched goes down from around 6.5 to 5.5 and ERA and WHIP both increase substantially. 

And that's as far as I'm willing to take it, because these are VERY SMALL sample sizes for every pitcher involved. For example, the leader in most games on short days of rest in the postseason is Roger Clemens--with 7. He's followed by Tom Glavine with 6 and Andy Pettitte with 5, making it extremely difficult to make grand conclusions. Add to that the fact these games are all against the best baseball has to offer and in a highly charged atmosphere and every sort of extraneous factor begins to creep in. In this instance, I'm merely presenting the data, because I'm not convinced the data MEANS ANYTHING.

But that doesn't mean there aren't interesting nuggets in the data. I found several instances where pitchers started games on short days of rest in more than two games--here's how the individual pitchers performed who threw three or more consecutive games on short days of rest:

I hope I didn't make this chart useless by including too much information, but I'd always rather err on the side of too much than too little. I just hope this isn't being read on a smart phone.

Many of these are remembered as among the best postseason performances in recent memory. Orel Hershiser's 1988 postseason dominance is well-documented, and many of the other performances that did not lead to victory for their teams were beyond blame to the pitcher. I also included the one odd performance, the one-batter appearance that Hershiser made in the middle of his five-game start streak.

 




I don't think it's an accident that these types of multi-short rest games are a relic of the past, with the last occasion being Curt Schilling in 2001 and prior to that almost another ten-year leap to the trio of Doug Drabek, John Smoltz and Tom Glavine. Pitching staffs are simply used in a different manner these days, and I suspect the addition of the wild card (and the extra games involved) leads to a desired reduction in wear-and-tear in the most important games of the year. That doesn't mean that occasions like what Kershaw accomplished don't arise from time to time--Hiroki Kuroda started consecutive games on short days rest in 2012 and Chris Carpenter, CC Sabathia and Justin Verlander all did in 2011. Between TV schedules, differing lengths of series and changes in pitcher use, it will be hard to string together more than two starts on short days rest. Like many other statistics, it's not necessarily that Clayton Kershaw or any other pitcher was able to come through with short rest as much as that he's a great pitcher--period.