The left-hander allowed a hit to Adam Eaton to lead off the game. Cliff Pennington then grounded to third, but Josh Donaldson could not handle it, and the ball scooted away. Eaton made a dash for the extra base, and Anderson went to third to cover, but the throw was behind him and jerked his neck away from the play as the runner slid into him.
Once Anderson got up from the ground, he felt the area located next to his right shoulder on his upper back stiffen up. A's manager Bob Melvin and the team trainer examined the southpaw on the mound before electing to remove him from the game.
"Obviously you want to get your work in," Anderson said, "but you don't want to overcompensate, change your mechanics and end up hurting your arm. So it was a precautionary thing."
Anderson added that if the injury had happened during the regular season, he would have thrown a few warm-up pitches to test it out, but the club did not want to risk doing so in Spring Training.
Back in the clubhouse, the pitcher was hooked up to a stimulation machine designed to help loosen up the knot. He said he expected to be stiff for a couple of days but hoped it would not delay his next outing.
"We're fairly confident he'll be all right to make his next start," Melvin said. "We'll know more tomorrow, but we're just happy it isn't anything serious."
Named the club's Opening Day starter in February, Anderson went 4-2 last season with a 2.57 ERA in 35 innings. Sunday was his second outing of the spring. In his first, he allowed one hit over two scoreless innings.
Tyler Emerick is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.