TAMPA, Fla. -- Right-hander Phil Hughes will be sidelined at Yankees camp after experiencing upper back discomfort during a defensive drill.

Manager Joe Girardi said that Hughes complained of stiffness behind his right shoulder after covering first base while the club's pitchers were taking fielding practice on Monday.

Hughes was sent to be examined by a doctor on Tuesday, and Girardi said that he expects Hughes to miss "a few days."

"There's always a little bit of concern," Girardi said. "It's [his] upper back, so we'll see how he is in a couple of days. The good thing is, he was ahead of where he'd probably normally be at this time, so it helps."

Hughes, 26, was 16-13 with a 4.23 ERA in 32 starts last season. This promises to be an important year for the hurler, who can be eligible for free agency after the 2013 campaign.

Phelps to start first Grapefruit League game

TAMPA, Fla. -- The Yankees have decided on their starters for the first two games of the Grapefruit League schedule, sending right-handers David Phelps and Adam Warren to the mound.

Phelps will be on the hill for the Yanks' first game on Saturday at 1:05 p.m. ET against the Braves in Lake Buena Vista, Fla., while Warren will pitch New York's home opener on Sunday against the Blue Jays at George M. Steinbrenner Field.

As preparation, both pitchers threw two-inning simulated games on Tuesday morning, shedding the protective L-screen as they pitched to Minor League hitters Cito Culver, Addison Maruszak, Corban Joseph and Ronnier Mustelier.

Phelps narrowly escaped a scary moment when Mustelier laced a hot liner back up the middle, forcing Phelps to twist out of the way as the ball slammed into a net placed behind the mound.

"I heard it. I didn't see it," Phelps said. "Robbie [Cano] probably would have had it."

Phelps added a positive scouting report on Mustelier, who hit a combined .314 with 15 homers and 69 RBIs in 114 games for Double-A Trenton and Triple-A Scranton/Wilkes-Barre last year.

"He's a good hitter," Phelps said. "He can swing it."

Girardi mulling over Grandy, Gardner swap

TAMPA, Fla. -- The Yankees still have not talked to Brett Gardner and Curtis Granderson about switching positions in the outfield this season, but a move is still on the table for manager Joe Girardi.

"I wouldn't read too much into what we've done yet, because we haven't played any games," Girardi said. "We still have time to discuss what we want to do, and I want to make sure our outfielders are versatile."

Girardi said that the Yankees are fortunate to have the flexible Ichiro Suzuki, who can play left, center and right. That could free them to use the exhibition schedule to try Granderson in left field and have Gardner patrol center field.

"It's something that, if we do start toying with it, we would do it very quickly," Girardi said.

Girardi said that the Yankees have still not reached a final decision on moving Granderson to left field. Granderson has said that he would be on board with a position switch if the club decides that is the course it wants to take.

"I think Curtis has done a good job for us," Girardi said. "The question for us to sit here and stew over is, 'If you flip-flop them, does it make you better defensively?' That's what we have to figure out."

Bombers bits

• Right-hander Mark Montgomery resumed playing catch on Tuesday. The touted prospect had been sidelined by back spasms.

• Eduardo Nunez figures to see a substantial amount of playing time at shortstop while Derek Jeter gets into baseball shape coming off left ankle surgery, but Girardi said that Nunez is still fighting for a roster spot.

"He has to earn it. That's the bottom line," Girardi said. "He has to earn it. We've got to toy with some different options, but we liked what he did at the end of last year. We know he provides a lot of excitement."

• Ichiro wowed the crowd at George M. Steinbrenner Field with a flashy behind-the-back catch during batting practice on Tuesday.

"I've seen him do it before," said Girardi, who'd prefer not to see it executed in a game. "Don't try that at home."