As it turns out, the Orioles not only blew a six-run lead on Monday against the Boston Red Sox at Fenway Park, they lost the right side of their infield for what could be an extended period.

Veteran first baseman Derrek Lee, who strained his left oblique in that game, was put on the 15-day disabled list Thursday. Second baseman Brian Roberts, who started Monday's contest with a head-first slide into first base to beat out an infield single, was put on the seven-day concussion disabled list.

Roberts has been experiencing headaches and concussion symptoms following the slide into first base. That raised concern after the 33-year-old second baseman missed the final six games last season with concussion symptoms that lingered well into the offseason.

Roberts would be eligible to come off the seven-day disabled list following Monday's off day. The seven-day disabled list was created before this season to allow injured players, team doctors and athletic trainers more flexibility in addressing head injuries.

"Anytime you're dealing with a concussion and heads and stuff, you're concerned about it," said Orioles manager Buck Showalter. "I was talking to Brian. This isn't anything like the symptoms he was feeling last year. That's good, but you still have those symptoms that we're going to make sure that we have our arms around it before we go forward. We're hoping that it clears up and the doctors feel fine about it, and he's a player on Tuesday."

Lee would be eligible to come off the disabled list June 1. However Showalter, whose club lost shortstop J.J. Hardy for a month with an oblique injury, said it is "iffy" that Lee will be immediately able to come off the disabled list when he's eligible.

"He came in [Wednesday] and talking to him, he felt some improvement and thought that he might be back. But from yesterday to today, it was about the same," Showalter said. "I don't want to lose Derrek. I'd like to have him. He impacts our team in a lot of ways, but taking a chance on this? The medical people think we could potentially take care of it during the DL period, but in my mind, that's iffy for me. We'll see. My experience with these things over the years, there is usually a lot more going on there than you think. I hope not. I think there's some talk about taking some form of an X-ray or something that shows certain inflammations to try and judge how bad it is."