Roy Halladay’s perfect game on Sunday was yet another great achievement from one of the game’s best pitchers. Halladay’s perfect game was the second such accomplishment during the month of May 2010. The other one was thrown Oakland Athletic pitcher Dallas Braden. Never before had two perfect gamesbeen thrown in the same season, let alone the same month. One measure of how significant this is that there have been entire decades including the 1910s, 1920s, 1930s, 1940s, 1950s and 1970s where fewer than two perfect games were pitched.

The most famous perfect game ever was pitched by Don Larsen in the 1956 World Series. Perhaps because of that, it is sometimes thought that perfect games are usually thrown by otherwise obscure pitchers. The truth, however, is somewhat different. Five of the eighteen pitchers who have thrown perfect games since 1900, Cy Young, Addie Joss, Jim Bunning, Sandy Koufax and Catfish Hunter are members of the Hall of Fame. One more, Randy Johnson will be elected in his first year of eligibility. Four more, Dennis Martinez, Kenny Rogers, David Wells and David Cone, are only one level down from being Hall of Famers, Mark Buehrle may also end up in this category as well after he retires. Thus, while previously unknown players like Len Barker or Don Larsen, throw perfect games, most are pitched by good or great pitchers.

Roy Halladay’s perfect game would seem to raise the question of where he fits in this taxonomy, specifically whether he is a great or merely very good pitcher. This, however, is not a serious issue. Halladay has been a great pitcher for most of his career who, barring injury or scandal, will almost certainly end up in Cooperstown along with roughly a third of the other pitchers who have thrown perfect games. His 135 ERA+, WHIP of 1.19 and five top five finishes in Cy Young balloting all are evidence that Halladay is a genuinely great pitcher. A more relevant question might be to probe the extent to which Halladay has been an outlier as a pitcher throughout his career.

Halladay has made his reputation by being not only a great pitcher, but by being a workhorse in a time when due to 12 or 13 man pitching staffs and stronger offenses, complete games are very rare. Halladay is on track to lead his league in complete games for the fifth consecutive, and sixth overall, time. Halladay leads all active pitchers with 54 complete games, only one other pitcher, Livan Hernandez with 48, has more than 32 complete games. Of the eight active pitchers with 25 or more complete games, only one, CC Sabathia is younger than Halladay. Sabathia is four years younger, but has 24 fewer complete games, so is unlikely to catch up to Halladay. Halladay is also the leader among active players with 18 shutouts. Only five other active pitchers have even half that many career shutouts; and three of those pitchers are older than Hallday.

Until the last few years, Halladay was one of the most unrecognized stars in the game. He played for a moribund Blue Jay franchise and rarely pitched in important games. His high profile trade to the Phillies and recent perfect game have changed that. Halladay now will likely have the opportunity to pitch in the post-season a few times, and to run up an even more impressive win loss record than the .661 winning percentage he had over twelve years in Toronto.

Nonetheless, Halladay occupies a strange place in the pantheon of great pitchers as his career fell between two generations of great pitchers. He spent the first part of his career in the shadow of the Roger Clemens, Randy Johnson, Greg Maddux and Pedro Martinez cohort who dominated the game from the late 1980s until the middle of the last decade and were all better pitchers than Halladay. When these pitchers began to retire few years ago, a new group of pitchers including Tim Lincecum, Zack Greinke and Felix Hernandez emerged as the top pitchers in the game. Although there is certainly no guarantee that these pitchers will have better careers than Halladay’s, it likely that for much of the duration of his career, Halladay will be not quite as good as at least some of this next generation of stars.

Lincoln Mitchell