Bill James did a piece a few years ago on Bert Blyleven in which he addressed the great mystery surrounding Blyleven's conspicuously mediocre W-L record. While conceding that Bert's critics make some good points - "Blyleven did not do an A+ job of matching his effort to the runs he had to work with" - he ultimately concluded that Bert's biggest problem was his lack of run support, not his failure to pitch better in critical situations. Bill attributed roughly two-thirds of Bert's relatively poor record to lack of run support and one-third to Bert's tendency to pitch relatively poorly in tight games.

Bill's analysis was disappointing in certain respects, however. First, he didn't note that Bert's relatively poor career W-L record is almost purely a function of his performance in the first nine years of his career ('70 to '78). Had Bert compiled a W-L record commensurate with his ERAs and run support in the '70s Bert would already be in the Hall and Bill James and I wouldn't be writing about him. Second, Bill didn't discuss Bert's pertinent statistics from this period that likely explain the disparity between Bert's excellent ERAs during that period and his pedestrian W-L record. As I've previously noted, Bert had terrible record in "late and close situations" in that period, far worse than any premier pitcher of that era that I've examined, and lost a disproportionate number of close games. While it strikes me as reasonable and logical to infer that a pitcher who performs poorly in the late innings of tight games will lose a disproportionate number of close games, I thought I'd look at the records of various pitchers in one-run games and attempt to determine if there is any significant correlation between a pitcher's performance in close games and his record in one-run games.

I began by identifying pitchers who either distinctly improved their performance in high-leverage situations or exhibited a distinct decline in performance in high-leverage situations.* I then compiled their records in relatively low-scoring one-run games in which they started and pitched at least 5 innings, reasoning that higher-scoring one-run games and games in which they pitched fewer than five innings are less a function of their performance and more a function of other factors. Accordingly, I looked at one-run games with scores of 4-3, 3-2, 2-1 and 1-0. A comparison of these one-run games to Bill James's data on all one-run games pitched by the pitchers referenced in his Blyleven article indicated no significant differences, meaning that none of the pitchers performed materially differently in higher-scoring one-run games.

Here are the pitchers in the two categories:

To begin with, one thing ought to be perfectly clear: you can't draw any inference from this list about who may be clutch and who may not. I don't care if Bob Gibson and Catfish Hunter exhibited a decline in performance in high-leverage situations - you can't tell me they weren't clutch.

Now, to the analysis. The six pitchers who improved in HL situations improved by an average of 7.5%, ranging from Guidry at 3% to Palmer at 13%. The nine pitchers who declined in HL situations did so by an average of 7.44%, ranging from Gibson at 2% to Rogers at 18% (I probably should have excluded Gibson, the only pitcher whose performance varied by less than 3%, but I left him in to make the point that this analysis is not intended to be any kind of dispositive argument about clutchness). The six improvers had a winning percentage of .614 in one-run games in which they started and pitched at least five innings. The six decliners had a winning percentage of .520 in such games. The correlation coefficient between performance in HL situations and one-run game winning percentage was a fairly strong .69.

There were outliers in each category. Ford improved by 6% in HL situations but had only a 32-29 record in one-run games (but, as with Gibson and Hunter, you can't tell me Whitey wasn't clutch). On the other end, Carlton and Sutton each declined by 12% but had winning percentages of .566 and .545, respectively. The best record in one-run games was Koufax, who had a winning percentage of .682 (and improved in HL situations by 6%). The worst record in one-run games was Blyleven, who had a winning percentage of .432 (and declined in HL situations by 6%).

This is obviously a very small sample set. There are more pitchers in the "decline" category than the "improve" category simply because that category seemed to fill out faster (primarily because I began by looking at pitchers referenced in James's Blyleven article and most of them just happened to exhibit performance declines in HL situations). I'm considering adding more pitchers to the analysis but compiling the records of one-run games is a fairly tedious exercise. If I can bring myself to pore through the game logs I'll update this analysis.
_______________________
* I opted to go with the high-leverage statistics at Baseball-Reference.com rather than the "late and close" statistics for various reasons but principally because the "late and close" statistics are just too narrow for this purpose, excluding anything before the sixth inning and even many situations in the late innings in which the difference in the score is only two runs. Additionally, "late and close" statistics have become increasingly less relevant over the last 30 years, as pitchers accumulate very few innings beyond the sixth inning. Whereas the "late and close situation" typically constituted between 15% and 20% of a pitcher's innings in the '60s and '70s, they generally constitute less than 10% of a contemporary pitcher's innings.