Outman, making his first big league appearance since June 19, 2009, allowed a run and five hits in seven innings after getting recalled from Triple-A Sacramento to make a spot start for injured Brandon McCarthy in the opener of a four-game series between AL West rivals.
But Torii Hunter threw out the potential go-ahead run at the plate in the seventh inning and doubled home the tiebreaking run in the eighth, leading the Los Angeles Angels over the skidding Athletics 4-1 on Monday night and overshadowing Outman's efforts.
Outman made 16 previous starts for the Athletics before missing last season while recovering from Tommy John surgery. The 26-year-old left-hander won his last four starts with the River Cats before getting recalled.
"I was pretty excited, but I was trying to keep my emotions under wraps," Outman said. "It feels like being at home. I feel like this is where I belong. I didn't prove that in the spring, but hopefully I can show over a period of time that this is where I should be."
It was the fifth straight game in which an A's starter allowed only one run, and none of those games resulted in a victory — the first time that has happened since the franchise moved from Kansas City to Oakland in 1968.
"That was quite an outing for his first time out," A's manager Bob Geren said. "Unfortunately, we couldn't get any runs for him.
"When you get one run, you have to be absolutely perfect as a pitcher. But it was a great outing and I'm looking forward to watching him throw again in five days. When you lose a couple of starters and have a guy come up here and step up like that, that's quite impressive."
A similar scenario will take place Tuesday night for the A's, when right-hander Guillermo Moscoso — who began the season in Sacramento — will make his first big league start in place of injured Tyson Ross.
Ross was filling in for Dallas Braden, who underwent season-ending shoulder surgery last week.
Bobby Abreu grounded into a fielder's choice after former Angels closer Brian Fuentes (1-7) opened the inning by walking Erick Aybar. Hunter greeted Michael Wuertz with a double to the wall in right-center on a 2-2 pitch, easily scoring Abreu.
Jeff Mathis capped the rally with a two-out, two-run single off Wuertz, who came in holding opponents to a .103 batting average — the best mark among AL relievers.
Fuentes has been charged with the loss in each of his last four appearances, setting an Oakland record. The A's have dropped six straight overall.
Scott Downs (2-1) worked a scoreless eighth, retiring David DeJesus on a groundout after giving up two-out singles to Hideki Matsui and Conor Jackson. Rookie reliever Jordan Walden pitched a perfect ninth for his ninth save.
Weaver failed in his fifth attempt to become the major leagues' first seven-game winner — this time with a hard-luck no-decision after four straight losses. The right-hander, whose previous victory was a shutout at Oakland on April 25, allowed one run and six hits over seven innings with five strikeouts and three walks against a starting lineup that had seven players batting .255 or lower.
"I think I just got off to too good of a start, so the expectations are high. I guess I'm back to being a normal pitcher," Weaver said. "But it's nothing I'm worried about. I'm just going to keep throwing the ball and let the chips fall where they may."
Weaver, the AL pitcher of the month for April, has one more chance to get his first victory in May. A loss or a no-decision next Saturday at Tampa Bay would make him the first major league starter to win at least five games without a loss one month — and then lose four or more the following month without a win — since July-August 2003, when current teammate Joel Pineiro did the swift about-face with Seattle.
The score was tied 1-all in the seventh when Andy LaRoche and Cliff Pennington singled against Weaver with two outs, and Coco Crisp lined a single to right field on a 1-2 pitch. Hunter charged the ball while third base coach Mike Gallego frantically waved LaRoche around, but Mathis slapped the tag on LaRoche while falling backward.
The Athletics had scored only six runs over their previous four games, so Gallego's decision to send LaRoche in that situation was the only one.
"I was all for it," Geren said. "The way it turned out, it was a close play and a pretty nice play by the catcher."
Los Angeles took a 1-0 lead in the first on an RBI single by Abreu. Matsui, who spent last year with the Angels, tied it in the third with a bases-loaded sacrifice fly — his first RBI against the Angels this season after 22 fruitless at-bats.
NOTES: The Athletics designated LHP Jerry Blevins for assignment to make room for Outman on the 25-man roster. Blevins appeared in 15 games with a 4.40 ERA. ... Moscoso, acquired in a trade with Texas in January, made 11 relief appearances for the Rangers over the previous two seasons with a 4.30 ERA. Opposing him will be former A's RHP Dan Haren, whose 1.84 ERA is the third-lowest in the AL. .