PHOENIX -- A day after declaring his right elbow pain-free and expressing optimism that he'd be ready to make a start during the first week of the regular season, A's ace Justin Duchscherer suffered a setback that could lead to him starting the season on the disabled list.

Duchscherer, who hasn't yet pitched in a Spring Training game, received a cortisone shot Saturday after feeling pain while playing long toss for the fifth consecutive day.

"It just didn't feel good when I was throwing," said the two-time All-Star. "This is ridiculous."

And more than a little ominous.

Before Saturday's workout, A's manager Bob Geren told reporters that Duchscherer was scheduled to throw off a bullpen mound Tuesday for the first time since being shut down for several days early in camp. He added that any sort of setback thereafter would rule Duchscherer out for the first week of the season.

Standing at his locker with a bandage on his elbow while the A's were beating the visiting Giants at Phoenix Municipal Stadium, Duchscherer said he was told he can't try to throw again for three days, so the earliest he'll be able to play catch is Wednesday -- on flat ground.

After the game, Geren said Duchscherer's setback essentially rules out the possibility of him getting in enough work to be ready for the first week of the season.

Because the A's need five starters right away, with 10 games in the first 10 days, they likely won't have the luxury of carrying Duchscherer on the roster if it's determined he'll miss more than one start. Geren, however, said he hadn't even thought about the possibility of Duchscherer needing to be put on the DL.

"I'm hoping he comes out Tuesday and feels good," Geren offered. "We're hoping this calms it down."

Dribblers: Nomar Garciaparra and Orlando Cabrera will be in the starting lineup Sunday against the host Angels, Geren said. Garciaparra will make his A's debut at third base, and Cabrera, who made his Oakland debut Saturday at designated hitter, will see his first action at shortstop. ... Third baseman Eric Chavez played catch for the first time since pain in his twice-repaired right shoulder prompted the A's to shut him down Monday. Geren said Chavez felt fine afterward. ... Reliever Joey Devine, also out with elbow pain, likely won't pitch in a game again for another week to 10 days. ... First baseman Daric Barton, out with a strained hamstring, is expected to return to action by the middle of next week.