Lewis has a strained muscle in his right side and was headed for an MRI exam today, while Alfonzo — injured in a collision at the plate with Oakland pinch-runner Donnie Murphy in the 10th inning to save a run — has a sprained ligament in his left knee that could require surgery and end his season.

"Whew," manager Bruce Bochy said today.

The Giants activated center fielder Dave Roberts two days earlier than scheduled from his rehab assignment with Triple-A Fresno at Las Vegas, three days shy of a month after surgery on his left elbow to remove bone chips and spurs. The club also brought up Guillermo Rodriguez to be catcher Bengie Molina's backup.

Roberts arrived only about two hours before game time and was in the starting lineup for the middle game of the Bay Bridge Series against the Athletics.

Molina was already out of the Giants' 5-3 loss yesterday on a double switch, despite his arm having gone numb after being hit with the ball. When Alfonzo was forced to leave the game with an injury to the posterior cruciate ligament in his knee, Bochy had no remaining position players on the bench. So, he moved third baseman Pedro Feliz to catcher, starting lefty pitcher Noah Lowry to right field and center fielder Randy Winn to third. Dan Ortmeier went from right field to center.

Alfonzo was still using crutches to get around today — and Bochy said he will be out at least two months even if he opts not to have surgery.

"There's nothing I can do," Alfonzo said of what happened. He plans to wait until Tuesday to make a decision on whether to undergo season-ending surgery, saying, "I don't know yet."

San Francisco had hoped to give Roberts a couple more days in the minors to work on his swing and get his timing back, and trainer Dave Groeschner plans to monitor him closely in the coming days. Roberts has been pain-free, which is encouraging to the club.

"The fact he is ready, we're pretty lucky," Bochy said. "We just had to rush him a little bit. He's good to go."

Lowry, who pitched Thursday's series finale at Arizona, struck out to end the game. Lowry, Feliz and Winn made their major league debuts at the positions they played in the 10th. Shortstop Omar Vizquel was "politicking," to catch according to Bochy, but Feliz was considered the best option.

"I didn't want it to happen, and that's probably why it happened," Feliz said. "I tried. You've got to do it."

Lowry took some popups in right during the game's short delay.

"I didn't do much," he said. "I just stood there."

The Giants were happy to have a fresh start today. The club lost two one-run games against the Diamondbacks in Phoenix, winning the series finale 5-4 on Thursday night in 11 innings to avoid a sweep at Chase Field.