VIERA, Fla. -- Lance Berkman was scheduled to travel with the Astros to Viera on Saturday, but a sore left shoulder forced the first baseman to stay back in Kissimmee, Fla., instead.

The setback -- officially diagnosed as tendinitis of the bicep in his left arm -- didn't appear terribly worrisome for manager Cecil Cooper.

"I don't think it's serious," Cooper said. "Rather than having him play and aggravate it ... he came in early this morning for treatment."

Darin Erstad played first base in Berkman's place against the Nationals.

In other injury news, Brandon Backe threw seven or eight minutes on flat ground Friday in Kissimmee, as did right-handed reliever Chad Paronto.

"I guess Paronto had less success than Backe did," Cooper said. "It wasn't quite as good as Backe's. We'll just have to try to get him ready, and get him right."

Backe is recovering from a strained left side that has kept him out of action for three weeks and knocked him out of the running for the fifth starter job. He'll begin the year on the disabled list. Paronto had an outside shot to win a spot in the bullpen, but realistically, with no jobs available, he's probably ticketed for Triple-A.

Also, infielder Edwin Maysonet was unavailable Saturday after experiencing soreness in his lower back. He first started feeling the pain during batting practice.

"It happened shagging," Maysonet said. "It was really sore in my lower back -- stiff."

Maysonet will be evaluated on a day-to-day basis.