PHOENIX -- Out sick Thursday and Friday, newly acquired A's shortstop Orlando Cabrera was back on the field Saturday, taking ground balls during the morning workout at Phoenix Municipal Stadium.

That's the good news. The bad news is that Cabrera's name has been added to Oakland's injury report, with tightness in his lower back.

"He's probably going to miss another couple of days," A's manager Bob Geren said.

Signed as a free agent on March 6, Cabrera made his Oakland debut eight days later and has hit safely in all three games he's played, going 4-for-9.

Geren said he had "no concerns" about Cabrera's absence.

"He did play 161 games last season," Geren said. "He knows how to get ready."

Former starting shortstop Bobby Crosby, who was moved into a utility role in the wake of Cabrera's arrival, saw his first action at shortstop since March 8 on Friday, but he started at designated hitter Saturday against the Giants.

"He's been playing a lot in the field lately," Geren said. "Just wanted to give him a little break."