PHOENIX -- Add center fielder Mike Cameron to the list of Brewers dealing with rib cage injuries.

Cameron tweaked a muscle between his ribs near his left armpit during relay drills on Wednesday and has been restricted from all baseball activity for the time being. He joins right-hander Braden Looper and catcher Angel Salome among the Brewers getting treatment on his rib cage.

"I had something like this two years ago and it lasted a month," said Cameron, referring to his final season in San Diego. "I don't want this one to be that way. I think we got it early."

The Brewers have been dogged by more than their share of injuries this spring, turning manager Ken Macha's morning briefing with reporters into a daily medical dissertation. Besides Looper and Salome, catcher Mike Rivera (right hamstring strain), outfielder Tony Gwynn Jr. (right shoulder) and third baseman Mat Gamel (right shoulder) remained limited to various degrees by physical ailments on Thursday.

However, Macha termed Cameron's injury "minor" and said he could be back in the lineup as early as Saturday.

"Injuries are going to happen in camp, and as the manager you can't let them bother you," Macha said. "So Cam's got a little rib cage [problem]. That means we'll see more of [Chris] Duffy. [Lorenzo] Cain is going to get his opportunity, and maybe he'll be ready for us in the middle of the year."

Duffy was slated to start Thursday's game in center field against the Padres. Cain started there against the White Sox on Wednesday.

"[Injuries] are like the weather," Macha said. "You can't control it, so don't even try."

Other injury notes:

• Third baseman Bill Hall, rehabbing a slight left calf tear, played five innings in the field during a Minor League scrimmage on Thursday morning. He's targeted to make his Cactus League debut this weekend, Macha said. Hall said he would like to play Friday against the Royals, but Saturday against the Dodgers is more likely.

• Backup catcher Rivera continued to take swings in the batting cage, but will probably not play in a game until the middle of next week. Salome has made better progress from a strained muscle in his back and could appear in Friday's game against the Royals.

• Looper experienced "nothing out of the ordinary" on Thursday, a day after he threw off a mound for the first time since suffering an injury to the left side of his rib cage. He will throw another mound session on Friday.