OAKLAND, Calif. (AP) — Bartolo Colon fielded a third-inning bunt and felt a sharp pain on his right side. He knew right away he was finished for the day.

"It felt bad," the Oakland pitcher said Sunday following a 2-1 loss to the San Diego Padres. "I had the same thing on my other side in 1999 with Cleveland and missed 28 days."

Colon, who will have an MRI on Monday, lasted two-plus innings — the team's shortest start of the year. He could become the seventh Athletics pitcher to spend time on the disabled list this season.

"It's tough to be without him, but he'll be back as soon as he can," second baseman Jemile Weeks said. "He'll be ready to go when he does come back."

Weeks struck out against San Diego closer Huston Street with runners at the corners in the ninth, ending Oakland's season-best five-game winning streak. Jonny Gomes had three hits for the A's.

"To not come through, or at least put the ball in play, is frustrating," Weeks said. "It's frustrating to somehow swing through a hittable fastball. I don't do that very often."

Street got four outs for his eighth save in eight chances. Clayton Richard (4-7) scattered five singles over 7 2-3 innings to earn his second consecutive win.

"He threw a great game," Padres manager Bud Black said. "He mixed in enough sliders, change (and) curveballs to keep them honest. But it was all about the fastball in good spots, throwing strikes and working fast."

Everth Cabrera scored on a groundout in the second and the Padres tacked on an insurance run in the ninth to salvage the finale of their nine-game road trip.

Oakland had two runners on in the second, fourth and sixth but Richard worked out of trouble each time to win for the second time in eight road starts this season.

"(Richard's) ball was running quite a bit, whether it was cutting or running," A's manager Bob Melvin said. "He made good pitches. Early on it was tough to see good swings. That shows his ball had late movement."

Street, the former Oakland closer, struck out Brandon Inge to end the eighth and had to pitch of a jam in the ninth after giving up an RBI single to Coco Crisp.

It was a tough afternoon all around for the A's.

After scoring 42 runs in the previous five games, Oakland managed only one — and might have lost another starting pitcher to injury.

Colon (6-7) pitched two hitless innings before allowing Cabrera's single in the third. Alexi Amarista followed with a sacrifice bunt that Colon fielded cleanly, but the pitcher threw wildly to first base, allowing Amarista to reach second while Cabrera raced to third.

As Colon walked back to the mound, Melvin and a team trainer came out to meet him. Following a brief discussion, Colon was removed from the game and replaced by Pedro Figueroa, who pitched three scoreless innings.

"At the time, that was big," Melvin said. "We weren't going to let him go beyond 40 pitches and he got through three innings with fewer than that."

NOTES: Before the game, the A's optioned RHP Tyson Ross back to the minors, one day after his spot start against San Diego. ... The A's have an off day Monday and will send RHP Brandon McCarthy (5-3) to the mound for the opener of a three-game series with the Angels on Tuesday. ... Gomes is hitting .438 (7 for 16) in nine June games after batting .222 over 22 games in May.

Copyright 2012 The Associated Press.