ARLINGTON -- They had to prove that they could win in this building.

To the rest of the division, fans, and maybe more than anyone, the Mariners had to show themselves that they could hang with the defending World Series champions at Globe Life Field after a disastrous showing here last season.

A 4-3 victory over the Rangers on Thursday afternoon that was a nail-biter until the end secured a winning series, the Mariners’ third straight after beginning the year winless in their first five, and lifted Seattle into sole possession of first place in the American League West (13-12).

Calling on any series or standings in April with significance is a stretch. But after going 0-6 here last year, missing the postseason by one game and trailing Texas by just two games in the division and AL Wild Card standings, this week’s effort carried weight.

“I just thought how we played was really important,” Mariners manager Scott Servais said, “to kind of establish like, 'This is who we are. We have a little bit of a different team this year. And we're very hungry.' I talked about that in Spring Training. You can talk about it all you want. You've got to go out and show it.”

Just as telling to the series win itself was how it manifested, especially in Thursday’s finale.

The Mariners were without J.P. Crawford, who was placed on the injured list with a right oblique strain pregame. They saw Luis Castillo labor into deep counts early, before righting himself to finish six strong innings of two-run ball. They also weathered one jam after another and escaped with another one-run victory.

There was the remarkable over-the-shoulder catch from Jorge Polanco while running back and the throw to the plate that held speedster Josh Smith at third base in the second inning. Instead of a run scoring, Castillo then grinded through a nine-pitch at-bat against Andrew Knizner and left runners in scoring position with a backwards K.

Then there was the inning-ending double play in the third that Luis Urías ignited on a 111.8 mph scorcher from Adolis García with two on and Castillo grinding. For good measure, Urías -- who’d been dealing with a bruised right hand after a hit-by-pitch on Sunday and limited with playing time in a third-base platoon -- crushed a two-run homer that put the Mariners ahead for good in the fifth.

“It's really hard, I've never been in [a platoon] before,” Urías said. “But I think it's not about me. It's about the team.”

And then there was Castillo zeroing in to retire each of his final eight batters after surrendering his second solo homer that tied the game at 2 in the fourth. Castillo was at 79 pitches through the fourth, putting his workload in peril for a deeper outing, but his quality start was Seattle’s AL-leading 14th.

“That's tough to do,” said Ty France, who crushed his first homer in the first inning. “He didn't have his best stuff early on, but to finish the game the way that he did, that guy doesn't shock me.”

But no jam was bigger than when Gabe Speier was called on to preserve a one-run lead and face Corey Seager with two on and two outs in the seventh. Seattle’s leverage lefty then induced a check-swing for strike three against the 2023 World Series MVP, ending Seager’s line in the series at 0-for-8.

“He did hit some balls hard that we caught,” Servais said. “But I thought we executed against him. Gabe did an awesome job. Hats off to Cal [Raleigh] sticking with a game plan and not getting away from it, trusting his stuff. A huge out in the ballgame.”

Moreover, Thursday marked the Mariners’ second straight win of the year in a rubber game after beginning the season 0-3 in those scenarios. They advanced to 11-3 when scoring first, underscoring the value of what their starting pitchers can bring when staked to a lead. They’re now 10-5 when hitting a homer and 10-4 when scoring at least four runs, showing what they’re capable of when the offense holds its weight.

As for Speier and Seattle’s relievers, over the three straight winning series, the bullpen has an MLB-best 1.01 ERA. But one incredibly telling stat is that the Mariners are now 12-0 when leading after the sixth inning.

The Mariners showed on this road trip that, even if they’re not at their best, playing close to it can create a winning formula.