The debate runs along two general paths. One side says, "Uh, I'm starting to get concerned here. We can't have a guy with a 6+ ERA taking the hill every five days if we want to be in the playoffs," and suggests that the Sox might need to make a trade (Seattle's Freddy Garcia gets mentioned often).
The other side says, "Derek Lowe has a great track record. He won 38 games over the last two years. He was great in the playoffs last year. Without Lowe, the Sox would have never made it into the Yankee series. You want to get rid of him after a couple of bad months?"
Those who know me can guess which side I'm on. I am concerned, definitely. Although I believe he's a talented pitcher and I'm not ready to dump Derek Lowe just yet, I wonder just how long the Sox can wait for him to right the ship.
For one thing, it's not true that we are looking at "just a couple of bad months" for Derek Lowe. Since the beginning of last season, I see just a couple of good months for Lowe. Lowe's month-by-month stats since the start of 2003 (W-L, ERA, WHIP):
Apr 3-2, 5.29, 1.58
May 1-1, 5.40, 1.57
Jun 5-0, 3.27, 1.21
Jul 2-1, 5.93, 1.65
Aug 3-2, 4.50, 1.31
Sep 3-1, 2.97, 1.39
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Pre ASB 10-3, 4.81, 1.48
Post ASB 7-4, 4.02, 1.33
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Playoffs 0-3, 4.18, 1.48 (1 sv)
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2004 4-5, 6.84, 1.93 (total)
It's not a happy trend that I see there. Lowe managed to "right the ship" last season, but the ship wasn't keeled over nearly as far as it is right now.
Also, when one considers that Lowe had a disappointing season in 2001 (when he lost the closer's job), we are now talking about one great season out of the last four. That begs the question, which is more indicative of Lowe's true talent level, the 2002 season or the 2004 season? I'm beginning to think that it's not the 2002 season.
Lowe's having all kind of problems this year.
In 2002, his K rate was 5.2/9IP, this year it's 3.7. In '02, his BB rate was 2.0/9IP, this year it's 4.4. That means that his k/BB rate has gone from 2.6 (good) to 0.8 (cow dung). Also, his GB/FB rate has gone from 3.5 to a career-low (other than his rookie year) 2.9. It was actually higher last year at 3.9.
It's generally accepted in the "sabermetric" community that Lowe's 2002 season was pretty lucky, in that he allowed far fewer hits on "balls in play" (IOW, anything other than a BB/HBP, K or HR) than would be expected. It's been shown that the vast majority pitchers have very little control over batting average on balls in play (BABIP) from year to year - because they can't control where the ball is hit (other than GB/FB).
The major league average BABIP is somewhere in the .300 range (.313 in the AL thus far this season, according to the Hardball Times at http://www.hardballtimes.com/main/statalpitch/), whereas Lowe's was .235 in 2002, which is very low. Lowe's career rate is .288, and he was at .294 last year. This year it's .357. Theoretically, we can expect this to move back toward .300, and Lowe will allow fewer hits. According to the stats page linked, Lowe's ERA based on his BB, K and HR rates "should be" 4.84 right now, which is 2 runs better than he's seen, but still not great.
Along with the high BABIP rate, Lowe's K rate is down (resulting in more balls in play), and his walk rate is up (resulting in more base runners), which are things that also need to be under control if he's going to improve much. In watching Lowe pitch, it seems obvious that his sinker is not sinking as much, and many balls that were once ground balls are now line drives. The one thing that the ERA estimator can not solve for is a high number of line drives. Line drives are much harder to field than any other ball, thus they fall in for hits at a higher rate. If Lowe is giving up an inordinate number of line drives (and it appears that he is), and continues to do so, that 4.84 is not a realistic number.
My assessment is that 2003 was about what you would expect from Lowe, based on his career BB, K and BABIP rates (a little worse, actually). Right now, I'd say that his 2003 numbers are a best-case scenario for this year, and I would be ecstatic if he posted a sub-4.00 ERA the rest of the way. Based on the all the evidence that I see, expecting Derek Lowe to return to his 2002 effectiveness is "pie in the sky" optimism. 2002 was Lowe's career year, he ain't gonna do it again.