In his one inning of relief, Runzler allowed two runs on three hits, including a home run.
"He was a little rusty, gave up some runs," manager Bruce Bochy said. "But the velocity was good, 92-94."
In 27 1/3 innings with the Giants last season, Runzler had a 6.26 ERA with 16 walks and 25 strikeouts. In 2010, he posted a 3.03 ERA with 37 strikeouts in 32 2/3 innings.
The Giants don't plan on just bringing up the lefty when he's ready this season, however.
"It's a baseball decision, as we need him," Bochy said. "This officially starts his rehab. So we have to make that decision once his rehab is over."