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5/17/2013 1:03 A.M. ET

Yanks hopeful tight upper back won't shelve Pettitte

NEW YORK -- Yankees left-hander Andy Pettitte was forced to leave Thursday's 3-2 loss to the Mariners after 79 pitches with a tight left trapezius muscle, which spans the neck, shoulders and upper back area.

Pettitte and manager Joe Girardi held out hope that he won't have to miss his next start.

Pettitte appeared to stiffen and wince after throwing his final pitch, a swinging strikeout of Kyle Seager for the second out of the fifth inning. Girardi dashed to the mound and held a fairly lengthy conversation with Pettitte, who shielded his mouth with his glove. Pettitte jogged off the field and was relieved by Shawn Kelley.

"Obviously, I'm realistic," Pettitte said. "I know how these guys are. I asked them if I could stay out there and try to get through it out there. I'm hoping it's a spasm and it settles down."

Girardi -- no stranger to injury updates in a season that has already been filled by them -- remained hopeful as well.

"I don't think Andy's [injury] is too bad," Girardi said. "His trap just kind of got a knot in it, and to me it was affecting his velocity. That's why I took him out. It's muscular, but I don't know what that means going forward." 

Pettitte, 4-3 with a 3.83 ERA, said that he never felt especially sharp on Thursday, allowing two runs and four hits, with three walks and five strikeouts to take the loss.

"It was just really tight," Pettitte said. "I couldn't get extended at all. I really just felt like I was kind of cutting everything off and just really trying to throw it in there almost slower than slow, to tell you the truth."

Pettitte missed a start in April with lower back spasms, but he said that he did not believe the two injuries were related. Pettitte turns 41 next month, but he said he is reluctant to use his age as an excuse.

"There's no doubt I'm getting old, but I don't want to sit here and tell you that that's the exact reason why, you know?" Pettitte said, with a chuckle. "I saw Moose [Mike Mussina] go through a full season at age [39] and win 20 ballgames."

The Yankees have already had 12 players on the disabled list this season, with 10 of those men still on the shelf.

Stewart could land on DL with injured groin

NEW YORK -- Yankees catcher Chris Stewart could be heading for the disabled list after injuring his left groin running the bases in Thursday's 3-2 loss to the Mariners.

Manager Joe Girardi said that Stewart was sent for an MRI after he had some trouble reaching third base on Robinson Cano's run-scoring infield single in the seventh inning.

Stewart was seen by Girardi and head athletic trainer Steve Donohue after reaching the bag and stayed in the game for one more batter, but he was replaced by Austin Romine behind the plate when the eighth inning started.

"When he went around the base and stopped, he said he felt something," Girardi said. "He said it didn't pop. He said he was OK, but when we saw him run, he said it continued to hurt."

Stewart has been assuming the bulk of the Yankees' catching duties since Francisco Cervelli went on the disabled list in late April with a fractured right hand. Stewart is hitting .265 with three homers and six RBIs in 24 games.

Girardi said that it was too soon to know if the Yankees would place Stewart on the disabled list, but it seems likely that journeyman Bobby Wilson would be first in line for a callup from Triple-A Scranton/Wilkes-Barre.

"You've got to move forward. That's the bottom line," Girardi said. "Injuries are a part of the game, and some years you're going to have more than others. Right now, we have a few and we have to move on. There's no excuses. You have to find a way to get it done."

Yanks fortify 'pen with Betances, option Marshall

NEW YORK -- The Yankees moved to bolster their bullpen's depth on Thursday, recalling right-hander Dellin Betances from Triple-A Scranton/Wilkes-Barre.

Betances, 25, had been touted as one of the club's brightest pitching prospects, ranked No. 19 by MLB.com, but the local product has experienced struggles with his control and recently moved to the bullpen full-time at Triple-A, where he was 3-2 with a 5.40 ERA in eight games (six starts).

"It's different," Betances said. "You get an adrenaline rush. It's fun coming out of the bullpen and trying to attack guys and throw first-pitch strikes. I enjoy the role. Whatever I'm needed to be, I'm here for."

Right-hander Brett Marshall, ranked No. 16, was optioned to Triple-A in a corresponding roster move, one night after Marshall saved the bullpen by throwing 108 pitches in 5 2/3 innings of long relief as he made his Major League debut.

Manager Joe Girardi said that Betances could provide the Yankees with length if they get into another wild game.

"He's done OK [at Triple-A]," Girardi said. "Your hope there is that he can simplify things and get on a roll and be a power arm for you."

Betances said that he was told about his shift to the bullpen by Minor League pitching coordinator Gil Patterson after he pitched five hitless innings in a win at Gwinnett on May 5.

The timing seemed odd to Betances, but he has been willing to accept the challenge if it helps his chances of contributing in the big leagues and said he feels "real close" to being back where he needs to be mechanically.

"At first it was hard. I'd been a starter since I signed," Betances said. "It's one of those things, but you kind of understand that situation. They said there's gonna be more opportunities out of the bullpen, so just go out there and compete. I took it all right. When the phone rings, I just get ready to go in."

Hafner encouraged after prodigious BP session

NEW YORK -- Travis Hafner resumed taking batting practice on Thursday, including launching a tape-measure homer into the second deck in right field, and the Yankees designated hitter said that his right shoulder is improving.

"Everything went really well," Hafner said. "I didn't have any of the issues I had before. I'm really happy with how it went."

Hafner had a cortisone injection in his right shoulder on Tuesday after an MRI examination showed tendinitis. Yankees manager Joe Girardi said that he might be able to use Hafner as a pinch-hitter on Thursday against the Mariners.

"I'm really encouraged by today," Hafner said. "Hopefully I'll be back out there soon."

Joba may be in line for another rehab appearance

NEW YORK -- Yankees right-hander Joba Chamberlain is not ready to be activated from the disabled list and could be assigned to make another Minor League appearance, manager Joe Girardi said on Thursday.

Chamberlain pitched a scoreless inning on Tuesday for Triple-A Scranton/Wilkes-Barre at Toledo and said he was not bothered by his left oblique, but Girardi said the Yankees aren't completely convinced.

"We're going to have him throw again," Girardi said. "Our concern is that he's just not quite ready yet. I think he's going to play catch again [Thursday], and then I'm not sure what the next step will be, whether it will be another bullpen or he will go on another rehab assignment."

Chamberlain has no record and a 3.86 ERA in 10 relief appearances for New York this season.

Yanks continuing to build Pineda's pitch count

NEW YORK -- Yankees right-hander Michael Pineda will throw four innings or 50 pitches on Friday in Tampa, Fla., working in either an extended spring game or an intrasquad game.

Manager Joe Girardi said that his expectation is that Pineda, who is returning from a labrum tear of his right shoulder, will pitch for the Yankees this season.

"We'll continue to build him up," Girardi said. "Starters, as you know, take a lot longer than relievers because you have to get them to 100 pitches.

"For a kid that hasn't pitched in a couple of years, that's something you may want to see a couple of times to make sure he's ready to go every fifth day."

Bombers bits

• Yankees right-hander Ivan Nova (upper back discomfort) is scheduled to resume playing catch on Monday, according to Girardi.

• Third baseman Alex Rodriguez took tee and toss on Wednesday in Tampa, Fla., and "felt pretty good," Girardi said. There has been no change in the Yankees' expectation that Rodriguez will be able to return some time after the All-Star break, and Girardi said it is "way too early" to project when A-Rod would be ready for a rehab assignment.

• Yankees shortstop Derek Jeter had a checkup on his fractured left ankle and has been told that the bone is healing. Jeter is expected to be cleared to remove his walking boot in the near future.

• Yankees third baseman Kevin Youkilis (lumbar spine sprain) has resumed swinging a bat, hitting off a tee and soft-toss, and and will move to taking batting practice shortly.

Bryan Hoch is a reporter for MLB.com. Follow him on Twitter @bryanhoch and read his MLBlog, Bombers Beat. This story was not subject to the approval of Major League Baseball or its clubs.