SEATTLE -- Last October, Lance McCullers Jr. walked off the mound in Chicago after giving the Astros four shutout innings against the White Sox in a series-clinching win in Game 4 the American League Division Series.

A flexor tendon injury in his right forearm suffered in that game halted his postseason and ultimately prevented him from pitching until Aug. 13, but McCullers returned to the playoffs on Saturday night at T-Mobile Park, once again in a series-clinching situation.

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McCullers delivered, and he did so in front of a thunderous crowd of 47,690 fans -- and that should come as very good news to the Astros moving forward to the American League Championship Series.

McCullers tossed six scoreless innings to kick off the Astros’ 1-0, 18-inning win over the Mariners in Game 3 of the ALDS, marking the second-longest scoreless playoff appearance in his career. Houston will need more of that in the next couple of weeks.

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“I was anticipating the crowd,” McCullers said. “I was excited. It’s kind of just, ‘Suck it up, use that energy for good and stay in control and go out there and win it.’ It was a rowdy environment. ... The Mariners played really great baseball this series. We were just a little bit better.”

With seven strikeouts, McCullers now has the second-most postseason strikeouts in Astros history with 69, trailing teammate Justin Verlander (96).

McCullers dominated the Mariners with a heavy dose of sliders, consistently challenging a Seattle team that has struggled to hit anything with high spin. He threw just 12 sinkers and two cutters compared to 46 sliders, good for the highest slider percentage of any game in his career (52 percent).

The Mariners whiffed 10 times at the slider, which was the second-most swings and misses McCullers has induced in any game of his career on the pitch. Three of his seven strikeouts came against Mariners rookie sensation Julio Rodríguez, who went down swinging on a slider in the first, third and fifth innings.

“The slider was good, yeah,” McCullers said, with a smile. “Had a little cross wind, maybe.”

Manager Dusty Baker said on Friday that the Astros are a different team without McCullers. It showed in 2021, when they were without both him and Verlander for the ALCS and the World Series.

After making his 2022 debut in August, McCullers posted a 2.27 ERA in eight regular-season starts. He hadn’t pitched since Oct. 3 against the Phillies before taking the mound in Seattle on Saturday.

Having a healthy and dominant McCullers back in the rotation changes the entire landscape of the Astros’ postseason run, and it puts them in an even better position than last year, when they won the American League pennant.

“Well, it says a lot,” Baker said of McCullers’ performance. “I would have had to fight him for him not to pitch, because he loves to pitch. He loves to pitch in these kinds of games and these scenarios. Boy, our pitching staff did a heck of a job here. [The Mariners’ staff] did a heck of a job, especially tonight on us, because it's hard to hold somebody scoreless for that long on both sides.

"This is some team. These guys, they grind, and grind and grind, and sooner or later, we broke through.”

Throughout the 18-inning marathon, the Astros’ bullpen matched Seattle’s blow for blow and capped it off with five stellar innings from Luis Garcia. Garcia and six Houston relievers combined for 12 innings of scoreless relief behind McCullers to complete the shutout.

Garcia allowed just two hits while notching six strikeouts to shut down the Mariners in the final five innings of the marathon matchup.

“Look at what Luis Garcia did tonight,” McCullers said. “Like, guys don't come out of the bullpen -- who haven’t pitched in two weeks -- and do things like that. It was a special night. Amazing, amazing performance. All around. Every guy we have is a great pitcher.”

“I don’t need to say anything [about the staff’s performance],” Verlander added. “They said it all tonight.”