- He may easily be ready right now, and the extra time in the minors might not do him a whole lot of extra good.
- The Giants need him in their rotation badly next year.
Let's compare Cain's debut this year with Noah Lowry's from last year (stat definitions at the end).
Lowry, 2004 (16 starts):
3.82 ERA, 92 innings, 91 hits, 1.33 WHIP, 7.04 k's/9, 2.57 k/bb, .728 OPS against
Cain, 2005 (6 starts):2.03 ERA, 40 innings, 18 hits, 0.88 WHIP, 6.08 k's/9, 1.59 k/bb, .526 OPS against
Lowry, with a much larger sample size, had a higher strikeout rate and a lower walk rate, which are good signs. Cain is somehow doing a marvelous job of simply not allowing hits (to the tune of a .133 BABIP), but that is something which can't and won't last over the course of a full season. For perspective, the ERA leader in the NL, Roger Clemens, has a BABIP of .236.
So in reality, our young Cain is getting lucky at this point, to some degree. I'll be looking for him to raise that k rate some next year, closer to seven per nine innings, and cut that walk rate down (it's currently pretty close to four per nine innings, which is higher than you want). Once he starts regressing to the mean as far as hits allowed, those extra baserunners due to walk will eventually cost him runs. Even though there's a large difference in their ERA's and OPS against, I look at Lowry's numbers as a bit more promising than Cain's in the comparison between Lowry's 2004 and Cain's not-quite-finished 2005.
However, there is still a bunch of obvious potential in Cain, and I think he is good enough to pitch in the big leagues next season -- although I wish he could put in one more year in the minors to really nail things down.
Stat Definitions: WHIP (walks + hits per inning pitched), k's/9 (strikeouts per nine innings), k/bb (strikeout to walk ratio), OPS against (on-base percentage + slugging percentage opposing hitters have earned against the pitcher), BABIP (batting average on balls in play)