SEATTLE -- The reports of Luis Castillo’s sudden fall from the elite class of MLB's starting pitchers might have been greatly exaggerated, but the importance of him returning to that stellar form on Monday night was not.

The Mariners needed Castillo to shine against the last-place A’s in the team’s first game back in T-Mobile Park after a long, grueling road trip. The right-hander delivered emphatically in an 11-2 victory.

At least for one night, the memories of Castillo’s previous four starts, in which he went 0-4 with a 5.73 ERA, allowed a .923 opposing team OPS -- including six home runs allowed -- seemed like fog in the rearview mirror. The Mariners' ace pitched six innings of shutout ball and gave up only four hits while striking out eight and walking two.

He also tucked another feather into his Mariners cap, notching the 1,000th strikeout of his career by punching out Shea Langeliers to lead off the fifth inning, and reveling in a standing ovation honoring the milestone.

“That's a lot, you know,” Castillo said through an interpreter. “Six years here in the big leagues, and hopefully God gives me the health to get 1,000 more.”

Castillo was aided by a breakout game from the Seattle offense. Jarred Kelenic’s two-run home run in the first inning got the Mariners started, and José Caballero hit a three-run shot in the second. Julio Rodríguez showed signs of emerging from his recent slump with a three-hit night, including two doubles and an RBI.

But from the very beginning, it was Castillo’s game. He threw first-pitch strikes to the first 10 batters he faced, finally throwing a first-pitch ball to Ryan Noda to lead off the fourth inning.

“The last couple of times, it's been a little bit of a struggle for [Castillo], but tonight he was super-aggressive, had all his pitches working, was locating much better, and really ahead in the count all night long,” Mariners manager Scott Servais said. “So a great outing by him.”

And even though the Mariners’ bats have been inconsistent this season, Castillo didn’t have to worry much about run support in this outing. In fact, there was a lot to be optimistic about when it came to Seattle’s hitters.

Kelenic got things going with a loud two-out, two-run home run in the first inning, blasting a Kyle Muller fastball 455 feet into the bleachers in right-center field. Caballero, who has upped his status from potentially-useful-late-bloomer to apparently-indispensable-piece-of-the-Mariners in a mere 24 Major League games, continued his 2023 joyride, making it 5-0 in the second by taking Muller deep into the Mariners bullpen in left for a three-run shot. It was Caballero’s second career homer and also his second in the past two games.

Kelenic, who played against Caballero in the Minor Leagues, said he’s not surprised by what his new teammate has been doing.

“The guy brings grit, and he's a leader on the team already,” Kelenic said. “And he's only been here for like a month now. But he's a guy that you need on a team because … he's going to go out and be the same guy, play the game hard every single day.”

Kelenic added an RBI single in the fifth and another hit in the eighth, and in another welcome sight for Mariners fans, Rodríguez had a bit of a breakout, going 3-for-4 with two doubles, including a laser of a line drive off A’s reliever Adrián Martínez in the bottom of the sixth that scored Seattle’s seventh run and registered an exit velocity of 109 mph.

Castillo had already departed after his turn in the sixth, and he finished with 98 pitches. The Mariners tacked on another run in the sixth on an RBI infield hit by Eugenio Suárez and three more in the ninth, two of them scoring on another Suárez single. Soon enough the Mariners (23-24) were dancing in the infield again as they climbed to back within a game of the .500 mark that has eluded them for much of the early season.

“We need to get it going and now's the time,” Servais said. “So it was great to see tonight. Again, it's just a start. You gotta go out tomorrow night and do it again the next night and do it again.”