To make room for them on the active roster, the A's optioned right-hander Arnold Leon to Triple-A Nashville and designated Andy Parrino for assignment, choosing instead to keep corner infielder Max Muncy in tow.
The A's have 10 days to trade, release or pass Parrino through waivers.
"Andy had his place for us, too, defensively, so it was a tough call," A's manager Bob Melvin said, "but we feel like Max will get enough at-bats."
Davis, who missed a month's worth of games with a strained left quad after hitting .282 in 33 games, was immediately back at first base Friday. He went 5-for-21 with five RBIs in five rehab games for Triple-A Nashville.
"It's great to get Ike back," Melvin said. "Reports are he had really good at-bats and he's fully healthy."
Mujica also enjoyed a successful rehab stint. The veteran reliever, who has been sidelined since May 22 with a fractured right thumb, appeared in two games with Class A Advanced Stockton and didn't allow a baserunner in two innings, striking out four.
It was just the type of performance the A's got from Mujica when he arrived May 9 via trade from Boston. He didn't allow a run in 5 1/3 innings before his injury, and his return undoubtedly bolsters the back of the A's bullpen.
"You always look to maybe get him a softer landing his first time back, but I don't know that that will be the case with him," Melvin said. "He's a veteran guy and was doing really well for us before he got hurt, so there's a chance you could see him in a very prominent role."
Melvin called on Mujica to try to squelch the Angels' comeback attempt on Friday night, but Mujica was unable to deliver during Anaheim's eight-run seventh. After Mike Trout reached on an error by Ben Zobrist, Albert Pujols crushed a grand slam off Mujica to turn a two-run deficit into a two-run lead. Mujica then struck out David Freese, and made an errant throw on Erick Aybar's bunt single before being pulled.
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.