Phils' rotation choice: Oswalt or Worley?

The Phillies sweeping the Braves this week wasn’t too critical in terms of outcomes. Both teams are already sure things when it comes to the postseason field. Things were closer earlier in the season, but that was before the Phillies reduced the regular season to a contest to see how far beyond 100 wins they will go.

If you’re looking for worthwhile takeaways, seeing Charlie Manuel’s club rally to win against the Braves’ bullpen on Wednesday night was impressive, but not for its beating Peter Moylan in the ninth to break a tie. What was more interesting was seeing the Phillies tie the game against Jonny Venters in the eighth. If Fredi Gonzalez were in the dugout (he’d already been ejected, after all) and if he used Moylan in a ninth-inning tie in a postseason series, that would be worth getting upset about -- then. But not so much in September, with little beyond single-series dignity at stake for the Braves, and after the Phillies’ sweep even that’s something best forgotten by the end of the first cup of Thursday morning’s coffee.

Instead, the really important takeaway from Thursday’s action was that Roy Oswalt made his latest case for October action while keeping pace with Vance Worley. At stake is who gets tabbed as the Phillies’ fourth starter in the postseason. In October, fifth starters get shunted to long relief duty if they’re fortunate, and to off-roster spectator status if they’re not. Manuel wasn’t shy about using Oswalt in relief in October last year, but it wasn’t as if putting him out there with two days’ rest after starting Game 2 was part of any master plan.

This time around, whether or not Oswalt will pitch out of the 'pen in the postseason will be a matter of choice. Oswalt’s injury-interrupted season has seen him deliver his worst strikeout rate of his career, down to 15.3 percent of all at-bats or 6.0 K/9. Pitch F/X data (via JoeLefkowitz.com, my favorite from among a bevy of fine sites) suggests that Oswalt’s velocity is down a lone mile per hour on his fastballs, sinkers and changeups -- not a lot, but with a lot more side-to-side wiggle in what are being labeled four-seam fastballs. More a matter of concern is the massive drop in the number of breaking pitches that Oswalt is using this year: In 2010, he’d throw a slider or curve 29 percent of the time, but this year it’s down to 19 percent.

While it’s a testament to Oswalt’s skill that he can still upset people’s timing by changing speeds while not working with the same full arsenal, the Phillies have September to sort out whether or not he can get back to being the Oswalt of old. Since he’s come back from the DL, he’s more closely resembled the ace acquired from the Astros, making six starts (including Wednesday's), five of them quality starts, while striking out a more characteristic 19.5 percent of opposing batters. But he’s also gotten hit, because even with Wednesday night’s no-hit bid (he took it into the sixth), he’s allowed 50 hits in 40 innings pitched. Blame the defense or blame the repertoire, but either way it’s not entirely reassuring.

Meanwhile, Worley’s been strong and getting stronger down the stretch. The Phillies have won all 10 starts he’s made since the All-Star break, getting seven wins for his troubles. Before the break, Worley was striking out 18 percent of his batters, but he’s up to 24 percent since. For comparison, the healthier Oswalt of 2010 was at 23 percent last year.

But at the same time that Worley has boosted his strikeout rate by a third, he’s cut his walk rate by a third, from 9 percent before to 6 percent in the second half. Even as he’s “regressing” with a second-half BABIP that’s slowly creeping toward league average, Worley has nevertheless been dominant because he’s using his defense less often, and putting fewer people on base by himself. His pre-break performance was very nice for a fifth starter on a good team, but if he keeps pushing toward four times as many strikeouts as free passes, he’s putting himself into the ranks of elite starters. He’s no longer “just” the fifth starter in the best rotation in baseball -- he’s becoming a pitcher to fear in his own right.

With three weeks of action to play, Oswalt and Worley are the two Phillies with something specific to play for. Before the World Series, there’s only one assignment fairly certain to go to either Oswalt or Worley: Game 4 of the National League Championship Series on Oct. 13. Sure, maybe the Phillies will have to play past three games in the first round, and there might be an extra-inning game or a rainout. But right now, that’s the only sure assignment, the prize for Oswalt or Worley to win, and watching whom Charlie Manuel picks and why is a lot more interesting than the Phillies’ final victory tally.


Christina Kahrl covers baseball for ESPN.com. You can follow her on Twitter.