Kaprielian (2-0) surrendered just two hits and two walks, striking out four in his third career start as the A’s snapped a three-game losing streak.
Matt Olson launched his 13th homer of the season and Seth Brown had two hits and two RBIs for Oakland. Ramón Laureano and Matt Chapman also drove in runs.
The A’s jumped on Seattle starter Robert Dugger for two runs in the first inning, including an RBI double by Brown. Dugger (0-1) allowed five runs on five hits and three walks in 3 1/3 innings.
Olson’s third-inning homer made it 3-0. He drove in another run in the fourth on a sacrifice fly as the A’s pushed ahead 6-0.
Jarred Kelenic, Mitch Haniger and Kyle Seager drove in runs for the Mariners in the eighth inning off Yusmeiro Petit. Jake Diekman came in to record the final four outs and earn his sixth save.
Oakland’s Elvis Andrus had two hits following a three-hit performance on Tuesday. The veteran has hit .308 over his last 17 games, raising his season average from .143 to .197.
“I feel a lot better at the plate, especially yesterday,” Andrus said. “I was able to find myself again and feel like myself like before. It’s been a really long, long process for me to be able to just feel comfortable at the plate. Hopefully, yesterday was a day to get me going and just continue to do that for quite a few months.”
Before the game, the teams held a moment of silence for the victims of a mass shooting Wednesday morning at a rail yard in San Jose. The shooter killed eight people before taking his own life.
“It’s awful,” Oakland manager Bob Melvin said. “And there are way too many of these things. It always hits home. It hits home more so when you are at home. It’s just awful. We play a baseball game today but this certainly is way more important than that. Hearts out to the families that have lost loved ones.”
Mariners: LHP Marco Gonzales, out since late April with a left forearm strain, was expected to throw a simulated game of 40 to 45 pitches this week. He could return to the rotation as soon as next week, though the team will be cautious. “You will not see him go out there and go six innings and 95 pitches the first time,” manager Scott Servais said. “No chance. We will slow play it and build him up as we go along.”
Athletics: DH Mitch Moreland (rib) could return before the end of Oakland’s current homestand. Moreland has taken batting practice and fielded ground balls in recent days. “He’s turned a corner and is doing everything at this point,” Melvin said.
Mariners: RHP Chris Flexen (4-2, 5.09 ERA) looks to beat the Texas Rangers for the second time this month as the AL West foes open a four-game series in Seattle on Thursday night.
Athletics: RHP Chris Bassitt (4-2, 3.69 ERA) takes the hill as Oakland welcomes the Los Angeles Angels for a four-game series beginning Thursday night. Bassitt beat the Angels on Saturday in Anaheim, allowing just two runs in 7 2/3 innings.