"I don't know what's going to happen," manager Lee Mazzilli said. "We need someone who can pitch Thursday."
The most likely candidate to take Chen's spot in the rotation is right-hander James Baldwin, who has been sparkling as a long reliever, allowing just one run in 13 1/3 innings. Triple-A prospect John Maine pitched five innings for Ottawa on Sunday, so he would be required to pitch on short rest.
Meanwhile, Bedard threw off flat ground for the first time Monday and did not feel any pain in the left knee, according to executive vice president of baseball operations Jim Beattie.
"We've learned more about Erik's injury and a better understanding of what could happen," he said. "I think we misspoke when we said two or three starts. He is going to need a period for rehabilitation starts as well."
Beattie said he doesn't see the club making sudden moves to compensate for the rash of injuries.
"I don't think we would do anything knee-jerk," he said. "That's not the smart thing to do. We're talking with (head trainer) Richie Bancells and monitoring the progress of our guys and determining our next move."
Beattie had no comment on a reported deal that would bring A.J. Burnett to the Orioles for Jorge Julio and Larry Bigbie. Outfielder Juan Encarnacion may also be part of the discussion in that deal.
"These days, you chase your tail a little bit with (the media) saying, 'This guy's available,'" Beattie said. "And you call the team and find out he's not available. We do our work on stuff, but the rumors are always going to be out there."
The club introduced third-round pick Brandon Erbe, a right-hander pitcher from McDonough School in Baltimore. Signing Erbe was a coups for the Orioles because he strongly indicated he was headed for the University of Miami. Instead, Erbe will begin his professional career for Rookie League Bluefield.
He threw in the bullpen Monday before the Orioles played the New York Yankees. The Baltimore native, who said he's attended more Orioles game than he could count, was thrilled with the experience.
"It was hard to keep my composure out there," he said. "It was extremely exciting. To put on that uniform and walk out on that field was amazing."
Draft experts have said Erbe may have fallen in the draft because he had already to committed to Miami. Orioles scouting director Joe Jordan indicated that the club took Erbe because he wanted to sign with his hometown team.
"I really wasn't expecting to get drafted by the Orioles more than any other team," Erbe said. "But when they did, I was really excited. I grew up an Orioles fan, admiring Cal Ripken, and to play in this field eventually will be a dream."
The club also signed fourth-round pick Kieron Pope, an outfielder from East Coweta High School in Gay, Ga. Pope has already reported to Bluefield.
Facing his first live batters since last September, Jason Grimsley pitched a scoreless first inning Sunday, allowing just one hit for Double-A Bowie in a 3-1 loss to New Hampshire. Grimsley allowed an infield single by Clint Johnston and three ground ball outs.
"I always get butterflies when I am out there," he said. "My control was a lot better than I thought because I was able to stay behind the ball and keep my head in there a lot longer."
Grimsley had Tommy John surgery last Oct. 12 and has made a remarkable recovery considering he was expected to miss the entire season. Grimsley will pitch Tuesday, Thursday and Saturday and then go consecutive days to determine his arm strength. There is a chance he could be back with the club in mid-July.
"We'll see how back-to-back days respond," Grimsley said. "But right now, I feel great. No pain."
Maine was touched for five earned runs in five innings as Ottawa dropped an 8-3 decision to Syracuse on Sunday in New York. Midre Cummings hit his seventh homer and also threw out a runner trying to score.
The Orioles take on the Yankees in the second game of a three-game series at Camden Yards on Tuesday. Right-hander Sidney Ponson (7-5, 5.42 ERA), who is 6-12 against New York lifetime, takes on right-hander Chien-Ming Wang, who has never faced the Orioles.