TORONTO -- Mike Mussina threw a light bullpen session on Sunday at the Rogers Centre, moving one step closer to taking the mound on Thursday for the Yankees.

At least, that's the plan. What will happen from here is anyone's guess.

That's because Joe Torre and Mel Stottlemyre haven't decided what to do with the starting rotation once Mussina comes back, as either Chien-Ming Wang, Jaret Wright or Shawn Chacon would be relegated to the bullpen.

"I'd like to believe we have a surplus," Torre said. "Looking at Thursday, Friday and Saturday and knowing we want to slot Moose in somewhere, you have to include [Chacon and Wright] in the mix, too. Or two of those three and Wang."

Wright, who started Sunday's game, left in the third inning after being hit with a broken bat, which could make Torre's decision easier.

Mussina wasn't pleased with his bullpen session on Sunday, but it had nothing to do with the elbow injury that has kept him out since his last start on Aug. 29. Mussina, who threw a simulated game in the bullpen on Friday, said his whole body was very stiff, which, in turn, affected his command.

"I couldn't throw the ball where I wanted to, and I got frustrated with how I was throwing it," Mussina said. "It's been a long time since I've pitched. Your body gets out of shape in a hurry."

"He's still getting back to where he needs to be," Torre said. "He needs to feel good about his command, because Moose is more about finesse than power."

Mussina, who threw 45-50 pitches at 50-75 percent effort, will throw another light bullpen session on Monday, putting him on track for a Thursday start. He said that he would likely be able to throw between 75-80 pitches in the start, which he hoped would get him through five or six innings.

"I'm not going to put myself out there in a situation where I can only go three or four innings and take somebody out of the rotation who can pitch six or seven," Mussina said. "Guys are throwing the ball pretty well right now, so I'm not going to ruin what we have going so I can throw three innings. In the situation we're in, that's not acceptable.

"Certainly there's some risk to it," he added. "I don't doubt that I could do it; the question is that, of the 75-80 [pitches], what quality will they be? That's the question. I could spin up 75 pitches in three innings, but that's not what we're looking for. The quality has to be there, and that's going to be a question mark right up until the game."

Giambi leaves game: Jason Giambi left Sunday's game with back spasms, but the injury isn't expected to keep the first baseman out very long.

Giambi felt his back tighten up in the second inning when he reached for a wide throw by Derek Jeter on an attempted double play. Giambi remained in the game in the third inning, striking out for a second time, and was replaced by Andy Phillips in the bottom of the fourth.

"He felt something," Torre said. "I don't think it's going to keep him out for long."

Giambi, who didn't speak with reporters after the game, said through a team spokesman, "I'm playing tomorrow."

With Tino Martinez nursing a rib cage injury since Aug. 31, Giambi has started each of the past 16 games at first base.

Unit staying put: Despite throwing just 50 pitches before his ejection on Friday night, Randy Johnson will remain on his regular five-day schedule and make his next start on Wednesday against the Orioles.

Johnson has three starts left this season, as he will take the mound on Wednesday, then on Sept. 26 in Baltimore and Oct. 1 at Boston.

On Saturday, Johnson said he might address his teammates as a group to apologize for being ejected from Friday's game. That meeting never took place, though he is believed to have spoken with several of his teammates one-on-one to discuss the incident.

Road warriors: When the Yankees left the Bronx last Monday, they traveled to Tampa to open a six-game road trip. Their road record at the time? 33-35.

But New York's 5-0 record to start the six-game trip has lifted them past .500 on the road, giving their postseason chances a boost.

"I think the equalizer when it comes to road games is [the bullpen]," Torre said. "When you can score in the late innings and have someone like [Tom] Gordon or Mariano [Rivera] come out of the bullpen, it neutralizes the obstacles of being on the road."

Entering Monday, the Yankees have seven games remaining at home before embarking on a seven-game road trip to close the season.

Bearer of bad news: On Saturday night, following the Yankees' 1-0 win, Torre had dinner with horse trainer Bobby Frankel. Torre received a call from Billy Crystal, who delivered the news that both the Red Sox and Indians had won their respective games.

"I had finished dinner and was very comfortable, so I said, 'Fine,' " Torre said. "From the scores of both games, I wouldn't have been comfortable watching them."

On deck: The Yankees open a seven-game homestand on Monday, hosting the first of four games against the Orioles.

Wang (7-4, 4.18 ERA) takes the mound for New York, while Erik Bedard (6-7, 3.82 ERA) gets the start for Baltimore.