Jed Lowrie has not been with the team since Thursday because of an illness that has left him fatigued.
The 25-year-old infielder has been undergoing a series of medical tests since.
"He just wasn't feeling real good," Francona said. "So we had him checked out by the doctor. We just want to run him through some tests before we get him back on the field. We've been doing that the last couple of days. ... He'll get some more tests tomorrow."
Francona said the tests were precautionary. Lowrie told Francona that he felt like he got hit by a truck.
"He just feels runs down and he said he's had this feeling during the winter at times. So we just want to get him kind of back on his feet and eliminate anything it could ever be. The safest way to go about that is run a bunch of tests," Francona said. "They did a bunch of stuff the other day, stress test and things like that. They'll do some things tomorrow and hopefully we'll get him back on the field as soon he gets all the results back."
The tests were administered in Florida. The stress test was in reaction to trainers noticing an accelerated heart beat.
"We're probably being overly cautious but I'm not sure you can be," Francona said.
Is Francona worried?
"When I say worried, I would think we think he's fine. He's been fatigued a little bit and we just want to rule out stuff," he said.
Lowrie has had only 10 plate appearances this spring. After spending much of 2009 on the sidelines with a wrist injury, his goal this spring was to prove he could stay on the field.
In other medical news:
* Josh Beckett will have his start skipped and pitch on Friday. That will keep him from getting as stretched out as the team would like. The result of that will probably limit him to six innings in his first regular-season start instead of seven. Tests were negative and Beckett appears only to be sick.
* Francona went with the ever-popular "we'll go day-by-day" when asked about Daisuke Matsuzaka.