BOSTON -- Red Sox pitcher Daisuke Matsuzaka has been sidelined with a stiff back two nights before arguably his biggest start of the season, the opener of this weekend's series against the Tampa Bay Rays.
The injury was detected, according to manager Terry Francona, when Matsuzaka went out to throw with pitching coach John Farrell between games of Wednesday's day-night doubleheader against the Seattle Mariners.
Francona said the Sox were unwilling to take the chance that Matsuzaka's condition would not improve in time to make Friday's scheduled start, so he quickly reshuffled the team's rotation. Jon Lester, who was to have pitched Wednesday night and had already begun his pregame routine, was told he was being held back until Friday.
"It kind of came in a hurry," said Francona, adding that general manager Theo Epstein was part of the conversation that included Matsuzaka, Farrell and Dr. Peter Asnis, a member of the team's medical staff.
"We kind of put the doctor on the spot -- what do we got?" Francona said. "He said he can't guarantee [Matsuzaka] will feel better tomorrow. It might go either way.
"The more we started thinking about it we thought, 'OK, we pitch Wake tonight, we back Lester up and we'll pitch Daisuke when he's able rather than have a game-time decision two days from now, or not have a pitcher.'
"We brought Lester in and explained to him what we were doing, and I thought Wake did a great job, especially under the circumstances."
Matsuzaka began the season on the disabled list with what was called a neck strain, though he actually was given time that he'd missed in spring training to build shoulder strength. He missed 23 games before returning on May 1. Six weeks later, he was back on the DL with what was called a forearm strain and missed an additional 14 games.
In his past nine starts, Matsuzaka was 3-1 with a 3.88 ERA, but had given up four earned runs in four of his past five starts.
Getting bumped from the Tampa Bay series may not be the worst development for the Sox. Matsuzaka is 0-1 with a 5.73 ERA against the Rays this season, and was knocked around for five runs (four earned), eight hits and four walks in five innings in his only start at Tropicana Field, on July 5.
Lester, meanwhile, is 1-1 with a 5.25 ERA against the Rays this season, holding the Rays to just one hit while striking out nine in six innings in his only appearance this season in the Trop, a 2-0 win on May 25.
Matsuzaka was not in the Red Sox clubhouse after Wednesday night's game.
Gordon Edes covers the Red Sox for ESPNBoston.com.