"Everybody knows Leonys is struggling a little bit," manager Scott Servais said. "I like the way Heredia is swinging the bat, and we’ll see him in there."
Heredia is 3-for-8 over the last two games, which puts him at .318 (7-for-22) for the season after winning a roster spot by batting .365 in spring training.
"He’s really improved," Servais said. "We saw it in spring training how his swing has tightened up. He’s driving the ball with a little more authority. He’s got kind of a knack for getting on base, too."
Martin is going in the opposite direction. He recently junked his new-look swing after a disappointing spring turned into a disastrous 6-for-54 start to the season. His on-base percentage is .172.
"We’re trying to play the best guys," Servais said, "the guys who are going best. Obviously, Heredia is on a nice little roll. It’s such a long season, and things turn. We’re trying to get somebody in there hot who gives us a little spark."
Martin has no options remaining, which means he can’t be sent to the minors to work on his swing.
Left fielder Jarrod Dyson switched to center field when Heredia replaced Martin in the lineup. Dyson had two hits Saturday in boosting his average to .242 and has reached base at least once in 16 of 18 games..
Club officials see the move as a wash defensively.
SEAGER SITS THEN HITS
Third baseman Kyle Seager also didn’t start Saturday but, unlike Martin, it figures to be a one-day break.
"These guys aren’t going to play 162 (games)," Servais said. "We’ll mix that in for other guys as we go along. We want to give those guys a mental break as much as anything. They’re really grinding right now."
Seager entered the game as a pinch-hitter and delivered an RBI triple — the 11th triple of his career. While batting just .246, his 11 walks boost his on-base percentage to .360. He had yet to hit a homer but has 12 RBIs in 19 games.
Mike Freeman replaced Seager at third base.
VINCENT LOCKS IN
Right-handed reliever Nick Vincent is back in form after a disappointing spring carried into his first few outings. He has retired 17 of 18 batters over 5 2/3 innings over his last five appearances.
Vincent also has eight strikeouts in that span.
"He’s probably our most reliable guy down there right now," Servais said. "That’s what we saw last year for long stretches.
"I don’t know how he does it, but there’s deception in there, and he has late movement on the cutter that is really effective for him."
Vincent allowed three runs and six hits over 3 2/3 innings in his first three outings after giving up five home runs in eight innings in nine spring games.
Three things to note heading into Sunday’s pitching matchup between right-hander Yovani Gallardo and and Oakland right-hander Andrew Triggs:
***Gallardo is 0-5 with a 5.29 ERA in six career starts against the Athletics, including 0-2 with a 3.71 ERA in three starts at the Oakland Coliseum. Triggs gave up five runs and six hits in two innings as a reliever last May 25 at Safeco Field in his only previous game against the Mariners.
***Yonder Alonso is 10-for-25 (.400) in his career against Gallardo, while Stephen Vogt is 3-for-6 with two doubles and a homer. Trevor Plouffe has two homers in 11 at-bats against Gallardo.
***Nelson Cruz and Robinson Cano hit home runs in Triggs’ only appearance against the Mariners.
Rehabbing reliever Steve Cishek wasn’t sharp Friday in lasting just two-third of an inning in a rehab start for Triple-A Tacoma. The good news is his problems were unrelated to his recovery from surgery to repair a torn labrum in his left hip.
"He felt fine," Servais said. "His release point, it wasn't coming out great. Nothing physical at all. It was a little more mechanical."
Tentative plans call for Cishek to make at least two more rehab appearances before being activated from the disabled list.
***Shortstop Jean Segura went 0-for-3 with a walk Friday as the designated hitter when he began a rehab assignment at Double-A Arkansas in his recovery from a strained right hamstring.
Plans called for Segura to further test his recovery Saturday by playing in the field. Barring setbacks, he is expected to be activated Tuesday from the disabled list prior to the start of a three-game series in Detroit.
It was eight years ago Sunday — April 23, 2009 — that Ichiro Suzuki led off the first inning with a home run against Tampa Bay’s James Shields, which turned into the game’s only run in a Mariners victory at Safeco Field.
Felix Hernandez pitched seven innings before David Aardsma and Brandon Morrow completed the shutout. Shields allowed just three other hits in 7 1/3 innings.
The Mariners and Athletics conclude their four-game series at 1:05 p.m. Sunday at the Oakland Coliseum when right-hander Yovani Gallardo (0-2 with a 6.19 ERA) opposes Oakland righty Andrew Triggs (3-0, 0.00).
Triggs has not allowed an earned run this season in 17 2/3 innings over three starts.
The game can be seen on Root Sports Northwest and heard on 710 ESPN and the Mariners Radio Network, including mariners.com (for subscribers to MLB.tv).
The Mariners have an open date Monday before resuming their three-city trip with three games in Detroit and concluding it next weekend with three games in Cleveland.
Bob Dutton: @TNT_Mariners