GM on Bay: He could be out 'quite a while'

Alderson, speaking before Monday night's game against the Orioles, said Bay, 33, underwent a medical examination Monday. He will continue to be evaluated Tuesday.

"I don't think we know how serious it is yet, and we may not know for a few days," Alderson said.

According to Alderson, Bay continues to experience symptoms related to his headfirst slide into the leftfield wall at Citi Field as he failed to catch up to a shot hit by the Reds' Jay Bruce that resulted in an inside-the-park home run.

He said of the recovery period, "Part of it depends on how quickly the more obvious symptoms dissipate. Right now, we're still waiting for all of those to clear."

Alderson emphasized the Mets' desire to avoid establishing any timetable for a return.

"The thing we don't want to do now is put any pressure on him to make him feel he's got to come back right away," he said.

Bay suffered his first known concussion when he crashed into the leftfield wall at Dodger Stadium on July 23, 2010, in his first full year with the team after signing a four-year contract worth $66 million. He was unable to return that season, finishing with six home runs, 47 RBIs and a .259 average in 95 games.

Although it was hoped that he would be a major source of offensive production when he finally returned to health, he hit a career-low .245 with 12 homers and 57 RBIs in 123 games last year. He struck out 109 times in 444 at-bats.

The Mets are proceeding as cautiously as possible. "When you have a knee injury, you wait until the swelling goes down before you make an evaluation," Alderson said. "In this case, I think we have to let things settle down a bit before you make an evaluation about when someone is going to come back."

Alderson said Bay was sent home to rest after visiting the doctor Monday and might be at Citi Field before Tuesday night's game against Baltimore.

On Saturday, Bay was placed on the seven-day disabled list, a category created to allow for proper evaluation of concussions.

Mets manager Terry Collins previously said he would not ask Bay to alter his pedal-to-the-metal defensive style, risky as it might be, because he would not want to take away his aggressiveness.