Stefan Romero's three-run homer off Evan Scribner gave Seattle a walk-off victory.
"I was just looking for something up to drive to get the sac fly," said Romero, who has never played above Triple-A. "Luckily, it went out."
Romero can play both corner outfield positions and has a real chance at making the big league roster when camp breaks this week. Manager Lloyd McClendon has taken notice.
"He's been playing well for about, say 2 1/2 weeks," he said. "Been swinging the bat."
Josh Donaldson and Derek Norris homered for the A's. Donaldson, who finished fourth last year in American League MVP voting, crushed a two-run shot off Mariners starter Randy Wolf in the fourth inning for his third homer of the spring.
Norris hit a solo shot off Wolf in the sixth and Cespedes added a solo homer off Yoervis Medina in the eighth that gave Oakland a 4-2 lead.
A's manager Bob Melvin was pleased to see cleanup hitter Cespedes, who finished 2-for-3 with a walk, go deep.
"When you're a power hitter, it's always nice to get that first homer out of the way," he said. "But his at-bats were better today. Couple of hits, a walk, a homer."
GRAY FOR OPENING DAY
Before the game, Melvin announced that Sonny Gray would be the A's opening day starter against Cleveland.
During his rookie season last year, Gray, a 24-year-old right-hander, started 10 games, posting a record of 5-3 with a 2.67 ERA and striking out 67 batters in 64 innings.
Athletics: Lindblom worked 1-2-3 innings in the first four frames before faltering in the fifth. After striking out Smoak and getting Seager to fly out in the fifth, Lindblom allowed his first hit -- a double to Morrison -- before Ackley homered to center. Lindblom scattered two earned runs on two hits, one walk and struck out three in 4 2/3 innings.
After the game, Melvin said Lindblom had been sent to Triple-A Sacramento to stretch out and be able to provide starting pitching depth for the Athletics.
"Now two down in the rotation, need some depth behind them," Melvin said. "Decision was either use him for length or stretch him out. We felt like right now we need to stretch him out and have him ready to start."
Melvin was pleased to see Lindblom mix in a slider to go along with a fastball, curveball and changeup in his arsenal.
"Today, I saw a better slider than we'd seen out of him," he said.
Mariners: Pushing for a spot in Seattle's starting rotation, Wolf had an up-and-down outing through six innings.
"He pitched better," McClendon said. "He was a little bit more crisp. Still made a couple questionable pitches that you just can't have when trying to win games."
Wolf worked quickly through the first three innings, allowing just one baserunner. He unraveled a bit in the fourth, giving up a leadoff walk and then the home run to Donaldson. Wolf scattered three earned runs on six hits and two walks, while fanning one.
Athletics: Relievers Ryan Cook and Fernando Rodriguez and outfielder Craig Gentry will begin the season on the disabled list. All three will only participate in minor league games through the rest of spring training.
Mariners: Corey Hart was held out of a game for the third day in a row because of forearm tightness and a sore biceps. McClendon said he wasn't too concerned and expects Hart to return Tuesday.
Hart, an outfielder and first baseman, could begin the regular season as Seattle's designated hitter.
"I'm not so sure how much right field he is going to play starting off, we'll see," McClendon said. "The goal is to keep him physically sound. And if DH'ing him is the better option, that's probably what we'll lean toward."
Athletics: Right-hander Murphy Smith was scheduled to make his Cactus League debut against the Texas Rangers at 1:05 p.m. Monday.