BOSTON – Last night’s scheduled starter, Tim Wakefield, was added – at least temporarily – to the Red Sox’s growing injury list.Wakefield (16-10, 4.16 ERA), who has been battling back tightness for more than a month, was a last-minute scratch with a sore back before last night’s game against the Orioles. The knuckleballer missed almost two months last year with a stress fracture in his rib cage. He is expected to miss one turn in the rotation, and not be placed on the disabled list.Julian Tavarez started in Wakefield’s place. It was Tavarez’s 22nd start of the season, but just his fourth in 11 appearances since July 26.Clay Buchholz, who likely would have been among the September call-ups, could get the start tonight against the O’s. The right-hander was scheduled to start tonight for the PawSox.Jon Lester is scheduled to start tomorrow’s series finale.Injury updates: Manny Ramirez received an MRI on his strained left oblique, the Sox waiting on the results.”The one thing I promise you is the minute he can play, he will,” Francona said.It is not known how long Ramirez will be out, but he could miss the six-game homestand.Before the game, Francona said Bobby Kielty, with a strained lower back, would be able to pinch-hit. Rather, he entered the game in the third when J.D. Drew departed with a contusion of his right foot after fouling a ball off an inning earlier.Catcher Doug Mirabelli, with a strained right calf, is eligible to come off the disabled list today.The call of September: With major league rosters set to expand from 25 to 40 today, several Sox minor leaguers will be getting the call within the next few days as their season winds down. All will likely be familiar faces, having appeared in a Sox uniform – or in a big-league uniform – before.As the team with the best record in baseball, in the stretch run with a playoff berth not yet secured, the Sox will likely not fill all 40 spots on the roster, as some teams do to give minor leaguers a taste of big league action or a reward for a good season.”We try to complement our existing roster with specific skill sets, such as a pinch-runner or defensive replacement,” general manager Theo Epstein wrote in an e-mail. “We don’t fill all the roster spots because having 40 active players is overkill and hard for (manager Terry Francona) to manage. There are off-season roster management issues that come into play as well. The hardest part is not always being able to reward all the Triple-A players who deserve the call-up.”Along with Buchholz and Lester, outfielder Jacoby Ellsbury is likely to be called up from today. Look for them to be joined by outfielder Brandon Moss, infielder Royce Clayton, and right-handed pitcher Devern Hansack. Right-handed pitcher Bryan Corey is a potential call-up. Longer shots are pitchers Craig Hansen, David Pauley, Craig Breslow, and Travis Hughes; catcher George Kottaras; or infielder Jed Lowrie. Clayton’s call would necessitate a roster move, since he is not on the 40-man roster.PawSox manager Ron Johnson will be joining the big league team after the PawSox season ends Monday and after he’s had some time at home with his family in Nashville.O’s move: The Orioles traded right-handed pitcher Steve Trachsel (6-8, 4.48) to the Cubs for third baseman Scott Moore and right-handed pitcher Rocky Cherry. Moore, 23, is expected to start for the O’s today, and Cherry, 28, is expected to be available in the bullpen.Joba the hurt: Yankees rookie pitching phenom Joba Chamberlain, who was immediately ejected from Thursday’s game after throwing two consecutive pitches over the head of Kevin Youkilis, felt the wrath of MLB again yesterday. He was suspended for two games and fined an undisclosed amount. Chamberlain began his suspension last night, against the Devil Rays.