FORT LAUDERDALE, Fla. -- The full extent of Jay Payton's left hamstring injury is still unclear, but the repercussions are beginning to be felt. Orioles manager Sam Perlozzo said Tuesday that it's a "realistic possibility" that Payton will go on the disabled list for Opening Day, which could cause a ripple effect in the lineup.

Designated hitter Jay Gibbons will likely see a lot of playing time in the field in Payton's absence, and reserve first baseman Kevin Millar could assume a regular spot in the batting order. All of that will revert back to form as soon as Payton's healthy, which could take anywhere from one week to a month.

"According to the trainers, it's a Grade I [strain]," Perlozzo said. "He's probably more than day-to-day. We'll try to hold off on him. I don't want to guess, but it's still sore. To me, that sounds like it's more than a couple of days."

Payton injured himself Monday while trying to advance from second base to third in a 4-2 win over Minnesota. He spent Tuesday morning getting treatment and said he's been afflicted with similar injuries before.

"I have to take care of my hamstrings. The only time I spent time on the DL was when I tore my right hamstring off the bone," said Payton, who missed almost two months with that injury in 1998. "This isn't like that. When I did that, I couldn't even walk. ... We'll just treat it [and] be aggressive with it -- but be smart. Hopefully, it won't be a month.

"It's just a matter of whether it will be a week [or] two weeks. It's kind of hard to tell right now. I can walk. I can feel it when I walk, but obviously I can't run. The main thing is to get the pain out."

Payton also had a less severe hamstring injury in 2001, but he's been relatively healthy since. The Orioles signed him this offseason to take over the vacancy in left field and to spell Corey Patterson against tough southpaws, but they didn't stand pat. They also inked Aubrey Huff, who was expected to start at first and push Millar to the bench.

Huff can also play the outfield, but the O's would rather keep him at first and push Gibbons into the field.

"Gibby played right field for us, and I thought he played it pretty decently," Perlozzo said. "I think Gibby doesn't look as smooth as some outfielders, but I also thought he got the job done for us. He feels comfortable, I think, in left field. He ought to be able to handle the position for a period of time without any problems."

The Orioles will likely open up that way, and Payton will spend the first couple weeks of the season working back to form. Perlozzo said that Baltimore will delay the disabled list announcement as long as possible in the hope that Payton can beat the injury, which is also the player's mindset at this point.

"I don't want it to be something that's going to linger," he said. "My preference is not to be on [the DL], but if that's what has to happen, it's better to be a little cautious now. I've got a week here that I'm not really missing any games, and if I have to miss a few games in the early going to be right, then so be it."

Labor day: The Orioles met with union representatives Tuesday as part of the Major League Baseball Players Association's annual tour of Spring Training camps. Baltimore closed its clubhouse for two hours and got a late jump on pregame preparation in order for the players to get a briefing from executive director Donald Fehr.

This year, in contrast to seasons past, Fehr had a rather relaxed itinerary to present. After all, with a new Collective Bargaining Agreement in place, there are few hot button topics that need to be addressed immediately. Fehr, who has just one team left to visit, wouldn't get into specifics but addressed the general tenor.

"These meetings are pretty tranquil," Fehr said to a flock of reporters. "Normally, we spend a lot of time talking about issues, and this is the first time in three or four decades we've got an agreement done before the old one expired. As a result of that, these meetings are pretty tranquil. It's nice to hear, and it's nice to go through."

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Ruled out: Adam Donachie, who worked with the Orioles as a Rule 5 Draft pick, was sent back to the Kansas City organization on Monday. Donachie was originally picked by the Phillies and then dealt to the O's for cash considerations and a different Rule 5 pick.

Baltimore tried but couldn't reach a deal with the Royals to keep Donachie in the organization. After that, the Orioles slid him through waivers with the intent of returning him to the organization that drafted and developed him.

"We certainly were hoping to keep him," said Perlozzo, speaking about the former second-round draft pick. "I think we tried to make a deal for him, but I think it was a little too steep."

Workout: The Orioles worked out Luis Martinez on Tuesday in the hope of signing the 6-foot-7 southpaw. Martinez hasn't pitched in North America since 2004, but he spent the '05 season as a reliever in Japan. Martinez was recently cut by the Washington Nationals, who had invited him to Spring Training.

"There aren't too many 6-foot-7 left-handers lying around that throw hard," said Jim Duquette, Baltimore's vice president of baseball operations. "We've had him in the past from 92-94 mph. He didn't throw that today, but he had thrown a side session yesterday, too."

Roster moves: The Orioles traded outfielder Corey Keylor to Boston on Tuesday in exchange for veteran catcher Alberto Castillo. Castillo will join the Orioles Wednesday and is expected to start the season at Triple-A Norfolk. The right-handed hitter is a career .222 hitter with 11 homers and 95 RBIs in 407 big-league games.

"He gives us some Major League backup help for catching," Perlozzo said. "He'll be at Triple-A, probably, and he'll help us out if we have an emergency."

Baltimore also optioned Sean Tracey to Norfolk and reassigned Jon Knott and Eli Whiteside to the team's Minor League camp in Sarasota. Seven players -- Mike Cervenak, Cesar Crespo, Steve Green, J.R. House, Andy Mitchell, Terry Tiffee and Ruddy Yan -- were reassigned but will remain with the Orioles through the end of the exhibition season.

Including Castillo, the O's have 31 players left in camp.

Quotable: "We certainly want to give Jay Payton every chance to wake up and say it's 100 percent better. That would probably be our ideal scenario." -- Perlozzo on the situation in left field

Coming up: The Orioles will play a pair of split-squad games on Tuesday -- one in Fort Lauderdale versus the Cardinals and one in Viera against the Nationals. Erik Bedard will start against St. Louis, and he'll be matched up against Braden Looper. Rob Bell will pitch against Washington's John Patterson. Both games start at 1:05 p.m.