Guerrero, who missed all three games of the Angels' sweep of the Mariners in Seattle, returned to Southern California on Wednesday along with Scot Shields to be examined by team orthopedist Dr. Lewis Yocum.
While Guerrero was cleared to play right away on a right knee that he hyperextended sliding into third base on Sunday, Shields was expected to get at least another off-day to recover from a strained left oblique.
An off-day Thursday refreshed a bullpen that has come alive of late with the tremendous work of rookie Jose Arredondo in front of closer Francisco Rodriguez, who leads the Majors in saves with 24 and is on a club-record run of 21 consecutive successful efforts.
"Vlad's OK," Angels manager Mike Scioscia said before engaging an A's club that came into the series having won four in a row -- one fewer than the streaking Angels. "We're going to DH him, work him back into the lineup. Everything checked out OK. Nothing new to report."
Shields, Scioscia said, "is feeling much better. It's a little tight still. We'll probably stay away from him tonight. We'll see how he is tomorrow after he throws some flat ground."
Sending Guerrero and Shields home to be evaluated were precautionary moves, Scioscia said, "to make sure we're not pushing guys into something they're not ready for."
Guerrero has been struggling to find a consistent groove, and the hope is that it will begin to come together in a park that has been among his favorites over the years.
In 30 career games at McAfee Coliseum, Guerrero has 13 homers and 31 RBIs with a .315 batting average. He has a .296 average with 18 homers and 52 RBIs in 68 games against the A's.
Guerrero hit only .219 in May, finishing in a 4-for-20 skid that left his average at .249 -- a career low for him this late in a season. He is seeking his 11th consecutive season with an average of at least .300 and a minimum of 25 homers. He would match Lou Gehrig (1927-37) for the record if he gets it done.
Shields, who began the season on the DL for the first time in his career with forearm tightness, hasn't pitched since Saturday when he worked one perfect inning against the Blue Jays to earn the win. He's 3-1 with a 3.27 ERA and is 10-for-10 in hold situations with a save in his only opportunity.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.