Mulling Over Splits

Anonymous wonders...

Is there a proper way to use Snell now--say in day games, away, when he'll face a bunch of righties?

I don't know how to address this question about Snell without looking at how accurate splits are in determining future success in these very same splits.

Top 10 Home ERAs 2008 (min 80 IP @ home)

#	Player	'08 Home	'08 Road	+/-	'09 Home	'09 Road	+/-
1	Jake Peavy	1.74	4.28	+2.54	3.58	4.60	+1.02
2	Rich Harden	1.79	2.50	+0.71	6.56	2.84	-3.72
3	Johan Santana	2.09	3.00	+0.91	2.18	4.79	+2.61
4	Derek Lowe	2.30	4.42	+2.12	3.27	4.84	+1.57
5	Cliff Lee	2.45	2.61	+0.16	2.21	3.83	+1.62
6	Jon Lester	2.49	4.09	+1.60	4.01	5.36	+1.35
7	James Shields	2.59	4.82	+2.23	3.07	3.72	+0.60
8	Odalis Perez	2.65	6.44	+3.79	N/A	N/A	-
9	Mark Buehrle	2.65	5.05	+2.40	2.68	3.83	+1.15
10	Jesse Litsch	2.77	4.32	+1.55	7.50	12.00	+4.50

With the exceptions of Harden and Perez, every one of these pitchers has also been better at home in 2009.

Not all of these splits are created equal, though. Lester's cratered across the board, but definitely isn't as dominant in Fenway this year as he was in 2008. Lee's only been dominant at Progressive Field, though many of his struggles came in his first couple starts of the season. I don't know what to make of the fact the Lowe has a 3.27 ERA at home; I thought that he was going to slip significantly this year because he was no longer pitching in the graveyard that is Dodger Stadium, but he seems to be getting a lift in Atlanta anyway.

In a few cases, these numbers kind of confirm what we already know. Peavy and Santana pitch in pretty favorable venues. Shields doesn't but - for whatever reason - seems to like pitching at the Trop.

There are also some surprises, though. Mark Buehrle pitches better at the launching pad he calls home? Litsch was that good in Toronto? Perez was that good anywhere?

If you are going to look at home/road splits, it is worth looking at at least two years worth of trendlines. Getting back to Snell's splits they look something like this:

2008 Day/Night: 7.71/4.64
2009 Day/Night: 2.53/7.21

2008 Home/Away: 4.50/6.22
2009 Home/Away: 5.76/5.12

2008 Left/Right: 911 OPS/805 OPS
2009 Left/Right: 870/841

For Snell, this year's numbers don't really follow any significant trends. He's a little better against righties, but his other numbers are putrid enough that I wouldn't start him against a righty-heavy line-up simply based on that.