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Some pitchers start off games better than others. I don't mean that Clayton Kershaw starts off games better than Luke Hochevar (though he does, of course), I mean that some pitchers perform far better in the 1st inning as compared to their overall numbers, while others do far worse.
Overall, starting pitchers do worse in the 1st inning than overall. Going back to 2000, starting pitchers have a combined ERA of 4.43, but in the 1st inning it's 4.77. For 2013 on its own, starting pitchers had a combined ERA of 4.01, but 4.24 in the 1st inning.
I suspect this is due in large part to the 1st inning being the one inning in every game in which a pitcher is assured of facing some of his opponents' very best hitters, but there's got to be more than just that going on, because there are pitchers with very big differences between their 1st-inning ERA and their overall ERA, including pitchers whose results have been far better in the 1st inning, despite facing the top of the order every time.
It takes a while to throw enough 1st innings for the total to amount to a sizable sample, but among active pitchers with 150+ 1st-innings pitched (almost enough to qualify as a full season's worth), you've got pitchers like Zach Duke (whose overall ERA is 4.47, but 6.82 in the 1st inning), Jeff Francis (4.94 overall, 6.96 in the 1st), and Paul Maholm (4.28 overall, 5.69 in the 1st inning), each of whom is significantly worse in the 1st inning, a much larger difference than there is for MLB starters as a whole.
Tom Glavine's career ERA was 3.54, but 4.58 in the 1st inning, and he started 682 games. It seems to me that there's something there beyond just facing the top of the order
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On the other side of things you've got pitchers like Scott Baker (who's overall ERA is 4.14, but just 2.72 in the 1st inning), Trevor Cahill (3.89 overall, 2.82 in the 1st), and A.J. Burnett (3.99 overall, 3.16 in the 1st). Those guys have all been significantly better than the average starting pitcher, in terms of relative 1st-inning success. I don't have a strong theory to explain such outliers, maybe some guys are just better at getting up to speed than others, or maybe even at that many innings, it's just white noise. I'm open to others' theories, if you've got one.
There's another trend which few can avoid, which is that each time they face a batter/lineup in a given game, starting pitchers become less effective.
Here are starting pitchers' results for each time they face a batter in a game (2000-2013):
| Plate Appearance | AVG | OBP | SLG | OPS | K/9 | BB/9 | HR/9 | ERA |
| Batter's 1st of game | .256 | .320 | .405 | .726 | 7.19 | 3.05 | 1.01 | 4.25 |
| Batter's 2nd of game | .269 | .331 | .431 | .762 | 6.38 | 3.06 | 1.12 | 4.43 |
| Batter's 3rd of game | .280 | .343 | .454 | .797 | 5.84 | 3.21 | 1.24 | 4.78 |
| Batter's 4th+ of game | .281 | .344 | .439 | .782 | 5.44 | 3.23 | 1.07 | 4.35 |
Here's the same data, but for only 2013:
| Plate Appearance | AVG | OBP | SLG | OPS | K/9 | BB/9 | HR/9 | ERA |
| Batter's 1st of game | .250 | .309 | .390 | .699 | 7.92 | 2.74 | 0.94 | 3.85 |
| Batter's 2nd of game | .259 | .319 | .411 | .730 | 7.12 | 2.86 | 1.04 | 4.05 |
| Batter's 3rd of game | .270 | .331 | .429 | .760 | 6.48 | 3.00 | 1.08 | 4.28 |
| Batter's 4th+ of game | .266 | .324 | .405 | .729 | 6.18 | 2.83 | 0.93 | 3.79 |
For one thing, those tables serve as a reminder that by 2013, offense had dropped substantially from where it was at the start of the century. You can also see pretty clearly that whether you're looking at a 1-year sample, or a 14-year sample, pitchers do quite a bit worse in their second time facing a hitter in a game, and quite a bit worse than that in their third time against them. I would guess that fatigue is the leading cause of declining production from starting pitchers as a game continues, but hitters may also begin to pick up their pitches better as they face them for the 2nd or 3rd time.
It may be surprising to see that in pitchers' 4th time facing a hitter they do so much better (in both tables), but consider that every start involves facing hitters for the 1st time, the vast majority of starts involve facing some hitters for a 2nd time, and most starts will include facing at least a few hitters for a 3rd time. Far fewer starts include facing hitters for a 4th or 5th time (In 2013 there were only 10% as many 4th+ PA innings as 3rd PA ones), and the ones that do tend to happen when a pitcher is doing very well in that game, so the 4th PA is heavily slanted towards better pitchers.
As I said above, this downward trend is one few pitchers can avoid. Later this week I'll look at how Indians pitchers have fared each time facing a hitter, and look to identify a few pitchers around the league who have held up better than most when they've worked deep into games.
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