As djslippyb pointed out in the comments section, Terry Francona is in the hospital due to chest pains.
"He experienced some chest stiffness earlier this morning," Boston general manager Theo Epstein said. "The best course of action was to take him to the hospital for precautionary tests."
Francona walked on to the ambulance.
"He had all his faculties about him, he was just going for tests," Epstein said.
According to Red Sox spokesman Glenn Geffner, Francona was resting comfortably and awaiting test results. And in what was perhaps a good sign, Francona was perturbed that he couldn't get the game on television or radio from the hospital.
The Red Sox expected to have more information regarding Francona's condition as the day developed. Epstein spoke with Francona by phone from the hospital.
"That's how [Francona] described it, stiffness in his chest," Epstein said. "We'll get more information for you as it's appropriate and available."
We wish you the best of health, Tito.