Second baseman Brian Roberts will not participate in baseball activities for the next two weeks and will be sidelined for a total of at least three weeks after seeing a concussion specialist in Pittsburgh on Tuesday.

"They recommend he not do any physical activity for two weeks and then get re-evaluated," Orioles president of baseball operations Andy MacPhail said. "He could come quickly after that or not, they don't know. But right now, the prescription is two weeks of inactivity and then re-evaluate."

Roberts suffered concussion symptoms in the first inning May 16 at Boston, when he slid headfirst into first base. He missed the end of last season after hitting himself on the helmet with a bat, causing a concussion.

He hasn't played since May 16 because of headaches, prompting a trip to sports-related concussion specialist Michael Collins in Pittsburgh. MacPhail said it's difficult to know how serious Roberts' condition is this time around but it's fair to say he'll be out at least an additional week once he gets back to physical activity.

"When you are dealing with these things, you don't know," MacPhail said. "Really, it's a science we're just starting to understand. We are just probably scratching the surface with that stuff. So you don't know."

Roberts, 33, is on the newly created seven-day disabled list for concussions. MacPhail said he likely will be moved to the 15-day DL for procedural purposes, but it doesn't alter his return, which all depends on how Roberts responds to rest.

"He is definitely improving, definitely better," MacPhail said. "You just have to let these things play out. There are, I think, different indications, different players, that historically went much further, much longer than people expected, and others came back relatively quickly. You have to take it individually."

Roberts was hitting .221 with three homers and 19 RBIs in 39 games. He has been replaced by Robert Andino and Ryan Adams at second base. MacPhail said he is open to other alternatives to fill in for Roberts.

"There are a variety of ways we can go," he said. "Particularly now, it is complicated because you have guys coming on the DL, off the DL, you don't know when they are coming off. There are some moving pieces, and I would suspect the roster is going to be in flux here for the next week or two as we make whatever adjustments we think we have to make to deal with it."