Ellsbury reinjured his ribs after he collided with Texas Rangers pitcher Tommy Hunter and then crashed to the ground on the first play of the game at Rangers Ballpark on Friday. Ellsbury was removed from the game after the top of the fourth inning.
He was sent back to Boston and had both an MRI and a CT scan taken at Massachusetts General Hospital on Saturday morning.
"The results showed some edema to the soft tissue in the same area, which suggest new trauma from the fall," explained Red Sox manager Terry Francona. "There's a faint line at the fracture site. It's impossible to tell [if it's] new or incomplete healing. You have to go on the symptoms and Jacoby says it's worse than [the first relapse in May] in Tampa, so we knew it was a DL."
Red Sox team physician Dr. Thomas Gill examined Ellsbury and indicated the injury is not worse than the original, and there's no way to predict how long it will specifically take him to return this time.
But Francona suggested Ellsbury's stint on the DL could be longer than the 15 days.
"We don't know, and Tom Gill was open about wanting to get more information," Francona said.
Ellsbury's scans will be sent to Dr. Lewis Yocum in Los Angeles for further examination. Ellsbury will remain in Boston unless Yocum wants to see him.
Ellsbury originally suffered five fractured ribs in a collision with teammate Adrian Beltre on April 11 in Kansas City. With Ellsbury back on the shelf, the Red Sox will use a combination of Ryan Kalish, Eric Patterson and Darnell McDonald in center field.
The Red Sox called up right-handed reliever Michael Bowden from Triple-A Pawtucket to replace Ellsbury on the roster.
With Francona having blown out his entire bullpen when Boston lost 10-9 in 11 innings Friday night, the right-hander is at Rangers Ballpark for Saturday night's game. This will be Bowden's second stint with the Red Sox this season, and he has not allowed a run in 2 1/3 innings of relief.
Joe McDonald covers the Red Sox and Bruins for ESPNBoston.com.