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08/28/10 7:05 PM ET

Berkman close, other Yanks progressing

CHICAGO -- The Yankees could be getting reinforcements off the disabled list soon.

Designated hitter Lance Berkman, out since Aug. 16 with a right ankle sprain, is scheduled to run on Sunday before the series finale against the White Sox. If all goes well, Berkman can be playing in a rehab game as quickly as Monday.

"It's good," said Berkman. "I can run around and do what I need to do."

Andy Pettitte, meanwhile, will throw another bullpen session on Sunday after his successful session on Friday. Pettitte will toss about 30 pitches from a full mound, although he's not sure exactly how much he'll push off the mound in testing his strained left groin.

For Pettitte, the major test will still be facing hitters.

"I don't think you can ever get the same intensity as a game," manager Joe Girardi said. "You can try, you can say I'm going to do it, but until you actually get in that game, you're not going to know."

Alex Rodriguez may start hitting as early as Monday, with the third baseman eligible to come off the disabled list on Sept. 5.

Finally, Alfredo Aceves was roughed up for the second consecutive rehab assignment on Friday night. Aceves tossed 1 2/3 innings, allowing three runs on two hits and two walks for Triple-A Scranton/Wilkes-Barre. In his previous outing, with Double-A Trenton, Aceves surrendered three runs on six hits (five doubles) in 1 1/3 innings.

"He was up in the zone and wasn't sharp," Girardi said, adding that Aceves has not had any physical issues. "We obviously want to get him back, and it's important that we get him sharp. We don't run him out there if he's not ready to go. He needs to continue to pitch until he gets there."

Girardi to look at rotation after weekend

CHICAGO -- Manager Joe Girardi reiterated on Saturday that he would evaluate his starting rotation after the weekend series with the White Sox.

"I said I'd evaluate after Sunday, and I'll stick to that," Girardi said. "Right now, the rotation is what it is."

That means Dustin Moseley and Phil Hughes are in line to start on Monday and Tuesday against the Athletics while A.J. Burnett's next turn on Wednesday remains a bit of a question mark.

Girardi, however, doesn't want to be too reactionary.

"You can't always evaluate everything when you're in a little bit of a struggle. You have to evaluate during good times and bad times," he said. "These guys have done it. They've done it over the course of the season. Right now, we're having some struggles."

The Yankees moved Javier Vazquez to the bullpen last week, after the right-hander was shelled by the Mariners. Vazquez has made one long appearance out of the bullpen since, and he could step in and take Burnett's turn if necessary. Sergio Mitre and Chad Gaudin are other candidates, with Girardi saying they could each throw as many as 75 pitches if needed.

Mitre tossed 4 2/3 innings of one-hit relief behind Burnett on Friday.

Burnett searching for answers to struggles

CHICAGO -- A.J. Burnett was as flummoxed as anyone following his latest poor start on Friday night, trying to figure out exactly what has caused his latest backslide in August.

"I'm just not getting swings on pitches I'm used to getting swings on," he said. "The balls they're hitting are just getting too much of the plate, I guess."

Burnett's problems for much of the season have originated from his inability to command his curveball. His bread-and-butter pitch last year, Burnett's curveball has been inconsistent throughout 2010. He has thrown it for strikes less frequently and not generated as many swings and misses on the pitch as in the past.

According to the pitching analysis of Texas Leaguers (using statistics from MLB.com's Gamdeday), Burnett has thrown his curveball for a strike 52.8% of the time this season, down from 56.3% last year. And hitters are making better contact against hit, swinging and missing on the hook 13.2 percent of the time this year, a decrease from the 16.8 percent a season ago. As a result, Fangraphs lists Burnett's pitch-type value with his curveball at 4.50 runs below average in 2010. For comparison, last year it was 16.0 runs above average, good for fourth in the Majors.

Burnett's troubles commanding his curveball mean he's falling behind more hitters, who can then spend more time sitting on his fastball. As a result, he's allowing a career-high 9.9 hits per nine innings while posting his lowest strikeout rate per nine innings since 2001.

"I was just behind a lot," Burnett said of his outing on Friday. "Some of the curveballs, they're good 0-2 curveballs, but what good does that do you 0-0?"

Manager Joe Girardi thinks Burnett's issues may be mechanical.

"Most of the times a pitcher's issues start mechanically. Something gets off a little bit, and it's harder to throw the ball where you want to," he said. "[With Burnett's curveball], that's somewhat of a mechanical thing where the arm slot gets a little bit too low. When it does that, it's not going to have that same bite down. Sometimes it may go across more or you'll leave it inside."

Girardi, though, still think there's time for Burnett to turn it around and regain the form that helped him pitch the Yankees to a World Series last autumn.

"He's done it before in his career where he's had struggles and he's come back and had long periods of time where he's been on track," Girardi said. "Sometimes it seems harder than others. It's basically the same principles."

Tim Britton is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.