Oakland manager Bob Geren said the move was mostly for precautionary reasons, and Anderson is not expected to miss any time. He's scheduled to start next Sunday against Los Angeles.
Anderson first reported some stiffness two days ago and was tight during warmup pitches on Sunday.
"I was just kind of monitoring it," Geren said after Oakland's 7-3 victory. "I thought his velocity was down a little bit. I thought they just missed a few balls. Just the total package -- talking to him in between each inning. It got to the point where I thought, for numerous reasons, he should exit the game."
Anderson threw four shutout innings against Tampa Bay, allowing three hits and one walk with three strikeouts. The 21-year-old rookie threw a complete-game shutout against Boston on July 6 and has allowed just one earned run in his last 18 1/3 innings.
But Geren did not want to take any chances with him on Sunday. Anderson was unavailable for comment after the game.
"The way it turned out, he was less than 100 percent physically and he gave a very good effort," Geren said. "He did a nice job, and players have to learn to do that sometimes, because they're not always going to be 100 percent."
A's catcher Kurt Suzuki said he thought Anderson looked good and didn't notice any dip in velocity.
Anderson will be Oakland's No. 4 starter after the All-Star break, following Dallas Braden, Trevor Cahill and Vin Mazzaro. He's 5-7 with a 4.64 ERA this season.
"It started getting to the point where I thought it was best to take him out, even though it was 0-0 at the time," Geren said. "I don't anticipate him missing any time."
Zach Schonbrun is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.