SEATTLE -- The Mariners finally gave Logan Gilbert some run support on Sunday afternoon, and only a marginal amount was all that the towering righty needed.

Under sun-soaked skies and in front of a sellout Father’s Day crowd, Gilbert dominated the Rangers over eight shutout innings to lift the Mariners to a 5-0 win at T-Mobile Park. Gilbert’s gem helped Seattle secure a weekend sweep over its division rival to cap a commanding early statement in the American League West.

Seattle advanced to 12 games above .500 (43-31) for the first time this season and extended its lead over second-place Texas to 8 1/2 games -- the largest division lead in baseball and its largest lead since it won the AL West in 2001 by 14 games.

The club hasn’t won the division crown since, and it has been playing -- and saying -- all season that it intends to hang another banner in the right-field rafters at T-Mobile Park.

Moreover, the Mariners, who have been in first place for 36 straight days, have now won 16 of their past 21 games dating back to May 26, easily MLB’s best record in this stretch, and they’re now 17-5 against the AL West.

“We're playing good ball right now,” Gilbert said. “When everybody's doing their job, we're definitely at our best. And that's what it looked like today.”

Thanks to some two-out run production -- the most chaotic coming from Josh Rojas scoring all the way from second base on a wild pitch in the fifth -- Gilbert cruised to a season-high 101 pitches and matched his best effort of the year dating back to a May 4 win in Houston, when he also threw eight scoreless innings. He punctuated the outing with a pair of strikeouts to Ezequiel Duran and Leody Taveras, storming off the mound screaming after.

On Sunday, Gilbert received his first run support since the top of the fifth inning in a May 25 outing at Washington, four starts prior. Before that, he hadn’t received a run of support since the bottom of the fourth on May 10 vs. Kansas City. In both of those games, the Mariners plated just one run, and for the season, he entered play averaging just 2.19 runs of support per outing, second-lowest among 74 qualified pitchers.

Gilbert’s teammates reached his almost guaranteed threshold for victory of three runs, as he is now 33-0 as the pitcher of record while receiving at least that many runs from his offense while he’s on the mound. Overall, the Mariners are now 41-9 in those outings for his career.

Gilbert leaned heavily on his slider, throwing it more than any pitch (38%) and generating a 1.6 mph uptick in velocity from his 87.8 mph season average. Going to the breaking ball early in counts also helped him masterfully set up his splitter for five of his nine strikeouts -- including in the first inning to Corey Seager, who remains hitless in 25 plate appearances against the Mariners this season after crushing them to a 1.133 OPS last year.

“It's a really tough at-bat,” Gilbert said. “I wish I had a good answer, but you really just have to go out there and make good pitches and mix it up and hope he's not guessing what you're throwing.”

Rookie first baseman Tyler Locklear -- who had a game-saving, diving grab for the 27th out in Saturday’s win -- cleared the three-run benchmark with a 390-foot solo homer in the seventh, to go with Rojas’ wild run and consecutive two-out doubles from Mitch Haniger and Luke Raley in the fourth.

Then after Gilbert departed, Seattle plated two insurance runs in the ninth, before Austin Voth locked down the final three outs to secure the club’s seventh overall shutout. That production, along with Gilbert’s length, proved all the more vital by allowing manager Scott Servais to avoid using closer Andrés Muñoz, who they’re trying to ease into action after he exited a June 4 outing at Oakland with a lower back strain.

“These guys like to work,” Servais said. “They like to prepare. They like to do the things that are going to give them the opportunity to perform on the biggest stage, and right now, they're doing it.”

Seattle now heads to Cleveland for a series that all of a sudden looks like a postseason preview. The AL Central-leading Guardians (44-25) currently hold the No. 2 seed, which comes with a bye into the AL Division Series, one spot ahead of the No. 3-seeded Mariners.