Jake Smolinski hit a three-run home run and drove in four runs and Chris Coghlan had three hits and two RBIs for the A's. Billy Butler doubled twice and drove in two.
The teams combined for 16 runs in the first 2 1/2 innings.
Sardinas, obtained in a trade with Milwaukee last November, is closing in on winning a major league roster spot with a .375 spring training average and the team lead with 30 hits and 14 RBIs.
Chris Iannetta had three hits and drove in four runs and Seth Smith had two hits and two RBIs for the Mariners.
Both teams' starters had shaky outings. Oakland's Jesse Hahn didn't make it out of the second inning, allowing seven runs and eight hits in 1 2/3 innings. Hahn is expected to be in the middle of the A's starting rotation but has allowed 13 earned runs in 10 2-3 innings this spring.
Seattle's Nathan Karns didn't fare much better. He allowed seven earned runs and eight hits in 2 1/3 innings.
''Not really much to say, just did not have his good stuff,'' Mariners manager Scott Servais said of Karns. ''It was one of the craziest spring training games. A lot of well-hit balls. We had a rough time with the shutdown inning tonight, I think is an understatement.''
Karns is trying to win the fifth spot in the Mariners' starting rotation.
''It's not ideal, but it's one of those ones where you kind of look at it and see what I need to do better,'' Karns said. ''I have to give them credit. They were able to beat me on some pitches that I thought I was putting the ball in the zone.''
Setup man Joaquin Benoit and closer Steve Cishek each threw a scoreless inning for the Mariners. Cishek struck out the side in the eighth and Benoit struck out two.
CANHA OF CORN
The A's Mark Canha played center field for the first time in the majors on Thursday and looked fine. Canha is normally a corner infielder and outfielder. He dealt with windy conditions and ran down Steve Clevenger's line drive to left-center field to end the bottom of the first. ''He looked really good,'' Hahn said. ''The ball that was hit in the gap there, the wind was really howling out tonight and the ball kept carrying and he got a really good jump on it, really helped me out right there.''
Manager Bob Melvin said he didn't yet know if Canha would get another start in center field in spring training.
A PLAN FOR PLAYING TIME
With spring training drawing to a close soon, Servais said the starting lineup will be playing more together in games over the final days of camp. ''Getting the back-to-backs, getting out there for nine innings, starting to get a regular season flow to their at-bats and to the game and playing together,'' Servais said. ''The same group playing together. That's what we look forward to over the rest of camp.''
Mariners: OF Franklin Gutierrez continues to deal with the flu and didn't play Wednesday night, as Servais had planned.
Athletics: Hahn tried to focus on the positives of his outing. ''I was doing things with my fastball. I just got hit. I just got beat out there,'' he said. ''I was very satisfied with my stuff. I was satisfied with fastball location . there's nothing much I can say about that.''
Mariners: Karns' ERA jumped from 3.29 to 6.75 after his fifth start of the spring. ''I didn't do a good job of working ahead and they did a good job of putting the ball in play,'' Karns said. He added that he hasn't found his rhythm yet but is confident he will soon.
Athletics: LHP Felix Doubront is set for his third start and fifth appearance of the spring. He was hit in the leg by a line drive in his last outing but stayed in the game. He faces the Rangers and former A's pitcher A.J. Griffin on Thursday.
Mariners: RHP Taijuan Walker is scheduled to pitch against the Colorado Rockies and Tyler Chatwood on Thursday. He'll be making his fifth start of spring training.