"I watched it about four or five times already and felt like I executed the pitch pretty good," Capps said. "I was trying to throw a strike low and away, and I did. He just got to it."
Mariners starter Aaron Harang gave up a run on five hits over seven innings. He walked one and struck out three.
The A's took a 1-0 lead in the fourth when Josh Reddick and Cespedes singled to open the inning and Donaldson had an RBI grounder.
Morales singled home a run in the seventh to tie it. He then cost the Mariners a chance to take the lead when he jogged into third standing up on Justin Smoak's sharp single to right field and was thrown out by Reddick. It was Reddick's 16th assist.
"I didn't realize it. I didn't know he was going to have a chance to throw to third," Morales said. "I was surprised about it. My main thing was thinking just to get to third."
Mariners interim manager Robby Thompson said third-base coach Darren Brown was telling him to slide.
"Obviously he should have been sliding," Thompson said. "I think he assumed that maybe Reddick was going to come up and throw the ball to second base. A mistake on his part. That's one guy you don't want to challenge, especially if you're kind of a below-average runner."
"I wasn't trying to throw the ball away," Parker said. "Instead of getting frustrated, I channeled the energy into making good pitches. That was kind of what I was thinking right there."
Harang made his major league debut in Oakland more than 11 years ago. Thompson played in his first World Series game in Oakland in 1989. "It's always special coming back to the Bay Area, especially staying over in San Francisco and walking around," Thompson said. "It brings back a lot of memories, no doubt. I spent a lot of time here. Had some good years here." A's manager Bob Melvin and Thompson were teammates in San Francisco. ... Seattle manager Eric Wedge is coming back from a mild stroke and is expected to be in uniform Friday in Seattle. ... Mariners OF Michael Morse missed his second straight game with a sore wrist. ... A's OF Coco Crisp was back in the lineup five days after getting a cortisone shot for his sore left wrist. ... A's LHP Brett Anderson will make his next rehab appearance Thursday at Class A Stockton.
11,112 (31.7% full) - % is based on regular season capacity
65 degrees, partly cloudy
Home Plate - Eric Cooper, First Base - Paul Schrieber, Second Base - Chad Fairchild, Third Base - Jeff Kellogg
Brandon Moss now has 4 career walk-off HR (2 this season).
All 4 of his walk-off HR have come vs. divisional rivals (3 for Oakland, 1 for Pittsburgh)
Jarrod Parker has allowed a .071 batting average in at-bats ending in his changeup in the second half, fourth best among pitchers who have thrown at least 50 changeups. Mariners batters have hit .173 in at-bats ending in a changeup in August, fourth worst in the AL.