Great piece by Rany Jazayerli on the mysterious formula of success of MLB pitcher Mark Buehrle.

In his 1984 Baseball Abstract, Bill James described “The Tommy John family of pitchers” as having “5 things in common.” James wrote:
1. They are all left-handed.
2. They are control-type pitchers.
3. They cut off the running game very well.
4. They receive excellent double-play support.
5. They allow moderate to low totals of home runs, lower-than-normal totals for a control pitcher.
This combination of abilities or tendencies enables this family of pitchers to be effective and to win at unusually high levels of hits per game, which then is another defining characteristic of the group.
Points four and five are essentially the same thing. James didn’t have access to ground ball/fly ball data 30 years ago, but he’s basically saying that Tommy John–style pitchers are extreme ground ball pitchers; ground balls lead to double plays and don’t lead to home runs. John himself allowed more than a hit per inning in his career, but many of those runners were wiped out on 6-4-3s.3
Buehrle would fit into the Tommy John family of pitchers perfectly, except for one small detail: He isn’t a ground ball pitcher. His career ground ball rate of 45 percent is just barely higher than league average, and thanks to spending most of his career at U.S. Cellular Field, he has surrendered 333 home runs in 3,009 career innings, a rate of exactly 1.00 per nine innings; John allowed 302 home runs in a career that spanned 4,710 innings. Thanks to all of those home runs in addition to hits surrendered on balls in play, Buehrle has allowed a higher batting average (.272) than John did (.265), even with a higher strikeout rate.

It's worth reading the piece to find out which two factors isolates as being enough to tip Buehrle over from failure to success, and just how fine that line is (as measured in outs and runs).