In his first at-bat of spring training, the slugger broke his arm when he hit by a pitch from Toronto's J.A. Happ in the bottom of the first inning Sunday, and is expected to be out until the first week of May.
"Grandy is not a bat you say is easy to replace, but we're going to have to find a way," Yankees manager Joe Girardi said. "No one is going to feel sorry for you."
The Yankees, who were beat 2-0 by a Blue Jays' split squad, first called it a bruise but X-rays revealed the break.
"Five pitches in we got a little setback," Granderson said. "Now we rest, recovery, get it back, and get ready to play whenever that day comes."
The team said Granderson could be out 10 weeks, which means he'll miss about a month of the regular season.
"Mentally, you understand this is part of it, but at the same time now there's not much I can do about it except do the best things I can to not make it worse," Granderson said. "Keep myself ready to go."
It's a major blow for the Yankees, who are already without Alex Rodriguez until at least the All-Star break. The Yankees also lost Nick Swisher to free agency.
Granderson led New York with 43 homers last season. The Yankees hit 245 homers last year and had five players with at least 20. This year they could open the season with just two players, Mark Teixeira and Robinson Cano, who topped 20.
Granderson was examined near first base before leaving the game.
"It didn't sound good," said Yankees third baseman Kevin Youkilis, who was in the on-deck circle when Granderson got hit.
The Yankees were planning to experiment during exhibition games to see if they would move Granderson from center to left, with Brett Gardner going from left to center. That potential alignment is on hold.
Girardi said that Gardner will likely start the season in center.
Matt Diaz and Juan Rivera, in the competition for the fourth outfielder spot, could see increased playing time.
"We'll be forced to take a look at a short-term option," Yankees general manager Brian Cashman said. "Obviously, we'll being get Curtis back. It's very early. We're still evaluating what we actually have in camp. The first month there will be a vacancy that we need to fill. Is that internal, external, I couldn't even tell you."
Cashman said he is not in favor of giving infielder Eduardo Nunez a look in left field.
Happ, coming back from foot surgery, went two scoreless innings, giving up three hits.
"The first inning, I was rushing a little bit, and not quite getting the extension I needed," Happ said. "Going out for that second inning I felt much better. I was taking my body toward home instead of first there."
Happ reached out to Granderson before the outfielder left the stadium for X-rays.
"Definitely not throwing on purpose, he's trying to work on coming inside," Granderson said. "It's a part of the game. Sometime you get hit. You just hope you get hit in a better spot."
Projected as the team's sixth starter, Happ had a 10-11 record with a 4.79 ERA in 24 starts and four relief appearances last season.
Yankees starter Adam Warren threw two hitless innings. The right-hander hit Brett Lawrie with a pitch in the second, which he said got away from him.
"Tried to go in with a fastball," Warren said.