He made his Major League debut with the Pirates in 2006 and has played all three outfield positions during his 107 games in the bigs, batting .252 with one home run, nine RBIs and 27 stolen bases in 36 attempts.
"He brings us a little different element with his speed," said A's manager Bob Geren, whose club entered Wednesday's game with five stolen bases in seven attempts. "Having a speed guy on the team is a nice addition."
Geren said he wasn't sure what his new outfielder's role will end up being, but Davis, who made several highlight-reel catches for the Giants last season, almost certainly will see plenty of time as a pinch-runner and/or late-game defensive replacement.
As for how many starts Davis might get, Geren said, "I'd like to see him play first. ... He plays left, center and right, and he's a good runner and good defender."
Geren said the decision to add Davis was not related to the health of struggling second-year outfielder Travis Buck, who was batting .154 through Tuesday and has been battling shin splints in both legs.
Buck hasn't started since last Friday, but Geren said Tuesday that the disabled list hasn't been discussed, and Buck on Wednesday said he didn't think a trip to the DL was imminent.
"It's not great, but I can play through it," Buck said before batting practice.
Saarloos, who was recalled from Triple-A Sacramento on April 14 and appeared in two games for the A's with a 2.35 ERA over 7 2/3 innings, must be traded, released outright or placed on waivers within 10 days. If he clears waivers, the A's would like to have him back.
"I'd like to keep him," Geren said of Saarloos, who also pitched for the A's from 2004-2006. "He's done nice work for us."