OAKLAND -- Red Sox designated hitter David Ortiz was admitted to Massachusetts General Hospital on Tuesday evening for tests to determine why he has experienced palpitations multiple times over a 10-day span. The big slugger remained in the thoughts of his teammates.

"You just hope that everything is OK," said Red Sox second baseman Mark Loretta. "Baseball kind of takes a back seat when you're talking about things of this nature. Obviously, we want him and need him, but we know that it's much bigger than baseball. They're going to do some tests and hopefully that will rule anything and put his mind at ease. Maybe it's fatigue or stress or a combination of the two."

Ortiz experienced stress, dehydration, lack of sleep and a rapid heartbeat on Aug. 18 and checked into Massachusetts General Hospital for observation the next day, where he was kept overnight and released with a clean bill of health.

When those symptoms cropped up again on Monday afternoon, the Red Sox immediately took him out of the lineup and set up more medical tests back home.

In a statement, the Red Sox said that the tests will be conducted over "the next few days," under the supervision of team internist Dr. Tom Ronan.

General manager Theo Epstein said that the club will release more information regarding Ortiz when it's available.

"I'll redirect you to that statement because it's a sensitive issue," Epstein said. "We don't want to be ahead of ourselves."

The earliest Ortiz would play again is Thursday night, when the Red Sox open a homestand against the Blue Jays. But the Red Sox aren't preoccupied with when Ortiz will be back in the lineup. They are putting all their focus into making sure he's healthy.

"He has to know that he's fine," said Red Sox manager Terry Francona. "We'll gladly put him in the lineup, but not until we know that he's not going to jeopardize his health."

Francona remained optimistic that nothing is seriously wrong with Ortiz, while making it clear that no stone would be left unturned in the quest for a definitive diagnosis.

Instead of moping about how poorly things have been going for the team of late, the players were putting their energy into wishing the best for Ortiz.

"I'm concerned as you would be if one of your close friends was sick," said Red Sox ace Curt Schilling. "I don't pretend to know the issues behind why and how. I just know how I want it to end up."

Loretta spoke with Ortiz in the clubhouse on Monday night.

"I've had some experience with it," Loretta said. "My mom has had some arrhythmia and gone through some things like that, it was stress-related. I was able to talk to David a little bit about that yesterday and he had some questions about it. He's in great hands. Harvard and Mass. General, I'm sure they've got some of the world experts in this situation, so he's in good hands."