The key is on-base-percentage (we're not gonna count errors, dropped third strikes, etc.). There has to be 27 consecutive outs. Also useful is that there are 3,240, and about 345,000 all time. For the stats savvy I'm also assuming that perfect games follow poisson statistics, which can be a dubious assumption for low end odds.
The following stats are against MLB average, Yankees (best team), Houston (worst), Justin Morneau (best batter), Aramis Ramirez(worst, of course), and with each of the three "perfect" game pitchers.
| Who | OBP | Expected | 3+ | All-time | |||
| MLB | 0.33 | 0.065247621 | 4.40885E-05 | 6.966794621 | |||
| Yankees | 0.366 | 0.01468774 | 5.22314E-07 | 1.568278894 | |||
| Houston | 0.286 | 0.363409878 | 0.006106128 | 38.80297759 | |||
| Morneau | 0.487 | 4.82741E-05 | 1.86517E-14 | 0.005154448 | |||
| A-Ram | 0.227 | 3.100211665 | 0.598882668 | 331.0241437 | |||
| Galarraga | 0.218 | 4.237672039 | 0.794695585 | 452.476124 | |||
| Halladay | 0.258 | 1.02671629 | 0.08528064 | 109.627315 | |||
| Braden | 0.277 | 0.509658225 | 0.015130549 | 54.41859965 |
Because you get to have good pitchers against bad teams every once in a while, I'd suspect the odds of the number of perfect games are roughly equivalent to Houston (there are 18 perfect games in the modern era, plus a couple others that might've qualified in these stats), so we should have three perfect games in a year once every 200 seasons (actually as low as every 100 because poisson stats are kinda inaccurate here). That's more often than you think? Remember, there's now 30 teams in the league, many more than earlier, so more games. Also, this year's league average OBP is the lowest since 1992 (although roughly average overall. Can you say steroids?).
And in good news for Galarraga, let's suppose he pitches 30 starts a year for 15 year (a solid career). If he continues his opponent OBP of .218 (the lowest among league starters), he has a 44.5% chance of pitching another perfect game. Of course, with an OOBP like that, he'll also be the best pitcher of all time.
Good suggestion Greg.
Great post, but what's the fuss? A lot of things have to go just right for a perfect game - that's why there aren't many. It is not all about the pitcher but about all the other people on the field being perfect for 27 consecutive batters - Not just 26 and not just the players. It didn't happen last night. Great baseball story, but not a perfect game - no matter what Bud would have said. (Bigger than Junior's retirement???) How often do we have 27 consecutive outs in a game, both sides combined?
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