SEATTLE -- The month of June has been rough on the Seattle bullpen, thanks in large part to a string of short outings from the Mariners' starting pitchers. In the span of eight days, Seattle made 16 roster moves involving pitchers.

On Saturday night, the bullpen played a huge part again -- this time in a good way -- as the Mariners jumped out to a big early lead and held on for a 5-4 win over the St. Louis Cardinals.

"It's really huge for us. It's huge for (the relievers)," manager Scott Servais said. "It gets their confidence back to hold that lead when it looked like it was slipping away from us there."

Six singles over the first two innings allowed Seattle (38-37) to pull out to a 5-0 lead before the Cardinals rallied to get within a run in the fifth.

Seattle relievers Mike Montgomery, Edwin Diaz and Steve Cishek finished off the game with four shutout innings to make the lead hold up as St. Louis (38-35) managed only three hits after chasing Seattle starter Nathan Karns (6-2) after the fifth.

Cishek gave up a one-out double in the ninth but got the final two outs to earn his 17th save of the season.

"Great job by our bullpen," Servais said.

Seattle had 10 hits, none of which went for extra bases. Center fielder Leonys Martin went 3-for-5, while Robinson Cano and Adam Lind each added a pair of hits.

Aledmys Diaz hit a three-run homer, and Yadier Molina and Kolten Wong had two hits apiece for the Cardinals.

Molina nearly had a third hit in the eighth, but Seattle third baseman Kyle Seager robbed him with a diving stop. Seager, who was charged with a costly error Friday night, got the Mariners out of a potential jam when the stabbed Molina's grounder down the line and threw to second to end the top of the eighth inning.

Seattle's Dae-Ho Lee and Lind, who have spent most of the season platooning at first base but are now in the lineup together, combined to drive in three runs as the Mariners took a 3-0 lead in the first inning.

Seattle had four singles and a walk in the frame -- all with two outs.

Lee drove in a pair of runs with a bases-loaded single, and Lind followed that with an RBI single off St. Louis starter Mike Leake.

The Mariners led off the second inning with back-to-back singles, then loaded the bases on a one-out intentional walk to Cano before an error and a groundout to second base resulted in RBIs for Nelson Cruz and Seager and a 5-0 Seattle lead.

Karns retired the first eight St. Louis hitters before the Cardinals finally got to him with two outs in the third inning. Two walks and a pair of singles, including an RBI hit from designated hitter Matt Holliday, allowed St. Louis to cut the deficit to 5-1. Karns got right fielder Stephen Piscotty to line out to second base to leave the bases loaded, ending the inning with minimal damage.

After Karns hit the leadoff batter and gave up a single in the fifth, Diaz delivered his 10th home run of the season that cut Seattle's lead to 5-4.

A fan jumped over the center-field fence and onto the field during a fifth-inning at-bat, barely interrupting play as a fly ball off the bat of the Cardinals' Matt Carpenter sailed in his direction. Seattle left-fielder Seth Smith, ignoring the fan who ran under the path of the ball, made the catch before Safeco Field security ran out and tackled the intruder behind the infield dirt.

"Crazy play," Servais said. "In the middle of the action, you don't usually see that. ... (Smith) kept his composure."

Leake (5-5) only made it through 3 1/3 innings, having allowed nine singles and a pair of walks while being charged with five runs (four earned).

"It wasn't a good day of pitching," he said. "It was elevated pitches and (the Seattle hitters) finding holes. Ultimately, it was just not locating the ball enough (in the strike zone)."

Reliever Tyler Lyons tossed 4 2/3 innings of scoreless relief, allowing just one hit, to keep the Cardinals in the game.

"Tyler was great," St. Louis manager Mike Matheny said. "It was very impressive."

Karns pitched five innings for Seattle, allowing four runs and five hits.

NOTES: St. Louis manager Mike Matheny announced before Saturday's game that reliever Trevor Rosenthal would no longer serve as closer. Rosenthal, who had been the Cardinals' closer since 2013, has blown three saves in May and June, the latest of which came Friday night in Seattle. Matheny did not name a new closer, but RHPs Seung Hwan Oh and Jonathan Broxton appear to be options. ... Cardinals 1B Matt Adams (back) was not in the lineup for the second day in a row Saturday. Adams was a late scratch for Friday's game because of back spasms, and he sat out Saturday's game as well. ... The Mariners are 8-1 in interleague games this season. ... Seattle 3B Kyle Seager had hit safely in each of his eight interleague games with a .531 batting average and 13 RBIs before going 0-for-3 on Saturday. ... Seattle has yet to name a starter for Wednesday's game against Pittsburgh, and there could be a few options. LHP Wade Miley is eligible to come off the disabled list Tuesday and could be back in the rotation. RHP Taijuan Walker skipped his last start with a sore ankle but shouldn't be out long. And LHP Wade LeBlanc added his name to the list of options when he threw six scoreless innings in his Mariners debut Friday night.