Garland, projected as the Dodgers' fifth starter, may have injured his oblique, manager Don Mattingly said.
"I don't think he's willing to say that until he gets the results, but he seemed to be leaning that way," Mattingly said.
And, he added, oblique injuries generally are "not a two-week thing, for sure." Rather, they normally take longer to heal.
The Dodgers already are without key pitcher Vicente Padilla. In the first days of spring training, the right-handed Padilla had surgery to repair a nerve trapped by a tendon in his pitching arm.
Padilla could miss the first month of the regular season.
Fister brought a 7.20 ERA into the game after two outings. He said he worked mostly on throwing fastballs for strikes.
"I felt like I would be a lot better this time," he said. "It's a stepping stone."
"I kept the ball down. I wasn't focusing on side to side, more down, working the middle of the plate, he said.
Mariners manager Eric Wedge liked it.
"I was really happy with the way he threw the ball today," he said. "He controlled the ballgame, did a good job moving his fastball around. He had a good tempo, and his secondary stuff was good."
Dodgers pitcher Hong-Chih Kuo made his spring debut. Last season, the All-Star left-hander posted the best single-season ERA ever (1.20) for a Dodger pitcher with a minimum of 50 innings.
Kuo pitched one inning, striking out one while giving up a solo homer to Jack Wilson.
The Mariners hadn't hit a homer in their previous seven games, but hit three overall against the Dodgers. Jack Cust hit a two-run shot and Alex Liddi had a grand slam.
Gabe Kapler played right field for the Dodgers in place of Andre Ethier, who had been scheduled to start. Mattingly said Ethier didn't understand he was supposed to be in the lineup. "I don't know what happened to him. I don't think he read the card," he said. "I guess in his mind he thought he was off, and he was in the weight room. I didn't want to take a chance on running him out there without him getting loose. Obviously, it was a misunderstanding. He wouldn't do it on purpose." ... Chone Figgins had two hits for the Mariners. ... Dodgers Hall of Famer Sandy Koufax visited the LA camp before the game.