CHICAGO -- Kirk Saarloos filled a variety of roles on Oakland's pitching staff during his three years with the team from 2004-06, from starting to long relief to closing on occasion.

On Monday, Saarloos was called up from Triple-A, catching a 7 a.m. PT flight from Sacramento to join the team for the opener of a two-game series against the White Sox at U.S. Cellular Field. And A's manager Bob Geren said Saarloos, a 28-year-old right-hander, again will be something of a Swiss Army Knife.

Oakland's rotation, however, is set for the time being -- even with righties Justin Duchscherer and Rich Harden on the disabled list. So Saarloos, who was 2-0 with a 2.45 ERA in two starts this season for Sacramento, will be used exclusively out of the bullpen for the time being.

That's fine by him. Saarloos, who spent the 2007 season with the Reds and their Triple-A club before signing a Minor League deal with the A's in January, prefers starting, but you won't find him complaining about his current assignment.

"I'd rather be in the bullpen here than starting in the Minors," he said with a smile.

Geren said he'd use Saarloos for "a hitter or two, to long relief and anything in between." Saarloos, who was scheduled to make his third start for the River Cats on Monday, hopes to use those opportunities to prevent a return trip to California's capital.

"It's all about coming here and competing," he said. "Coming into Spring Training, I thought I had a good chance of breaking camp with the team, but if you [get sent to the Minors] and start moping around, you have no chance. You're selling yourself short."

To clear room for Saarloos on the 25- and 40-man rosters, the A's designated for assignment righty reliever Fernando Hernandez, who was selected in the Rule 5 Draft out of the White Sox organization in December.

Hernandez, who posted an ERA of 18.00 in three appearances for Oakland, now can be traded or put on waivers. If he clears waivers, the A's have to offer him back to the White Sox. If the White Sox pass, Hernandez likely will be sent to Sacramento.

"We liked what we saw from Fernando," said Oakland assistant general manager David Forst. "He's just not a fit for this club right now. He had a really good spring, and he's got good stuff. ... Hopefully we can hold onto him."

Geren, who has had one lefty in his bullpen -- Alan Embree -- since Lenny DiNardo was plugged into the rotation last week, said he's sticking with DiNardo, Greg Smith, Dana Eveland, Chad Gaudin and Joe Blanton as his starting five until Duchscherer and Harden return from the DL.

Forst mentioned that Oakland's bullpen was a bit "taxed," making Saarloos' ability to pitch multiple innings particularly attractive, but Geren called Sunday's loss in Cleveland "big" for the bullpen because Gaudin and Hernandez were the only two pitchers used.

"We're pretty well rested down there now," said the skipper.