Anderson allowed five hits and two runs while striking out one over his two innings. He threw just 36 pitches, 23 for strikes. He left with his team trailing, 2-1.
"My fastball [velocity] wasn't there. My command was OK, but my slider just wasn't the same. There were a couple of at-bats where I had two strikes, and most of the time, I have a put-away slider, and I just couldn't get them there today."
Anderson said he didn't feel anything strange in warmups but once the game started, the uncomfortable feeling he had earlier in the season in the same part of his left forearm returned.
"First inning was OK, but second inning was a lot worse, and obviously, I couldn't go from there," Anderson said. "It was soreness and kind of like a recurring theme from what happened earlier in the year, but hopefully, I'll know more [Friday] when I see a doctor, but I hope it's not too bad."
X-rays taken during the game were negative, but he will be re-evaluated Friday when the team is back in Oakland.
In the bottom of the third, while attempting to make a sliding catch on a Kevin Youkilis foul pop along the right field line, Ryan Sweeney took a knee to the head from second baseman Mark Ellis and had to leave the game.
"He got hit in the head with Ellis' knee," Geren said. "He was a little disoriented, a little dizzy, so as a precaution, he was removed from the game."
Sweeney complained of dizziness to trainer Steve Sayles.
"I know when I went out there, he was dizzy, and Steve said, 'Take him out,'" Geren said.
Eric Patterson came into the game to play left field while Gabe Gross moved over to right field to take Sweeney's spot.