Farrell arrived here shortly before 5 p.m., accompanied by Red Sox medical director Dr. Larry Ronan. He originally had planned to manage Tuesday night's game, but moments before first pitch, team publicist Kevin Gregg announced that Farrell had returned to the team's hotel and bench coach Torey Lovullo was managing in his place.
"This was something that came up, reared its head on Friday," Farrell said. "After some tests on Saturday, it was determined that it needed to be taken care of Monday morning. Overnight in the hospital, I come down here.
"I won't win a sprint race right now, I'll tell you that, but we're here."
Farrell said he believes he injured himself tossing his equipment bag Thursday night in New York.
"Any kind of rotational burst or movement is what typically causes it," he said. "Seems to be the culprit, late Thursday night."