HOUSTON -- Astros pitcher Wade Miley stayed in the dugout nearly the entire time, supporting his teammates and giving congratulatory high-fives for more than four hours while the Astros chipped away to try to erase a seven-run deficit he had helped create.

Despite having one of the worst starts of his career -- he didn’t record an out while facing six batters -- Miley waited for a comeback. And waited and waited. The lefty had finally made his way to the clubhouse to finish watching the game on a television broadcast, which is delayed a few seconds from live action.

So when Miley heard the end-of-game fireworks boom through the clubhouse walls, he knew the day would end much better than it started.

Michael Brantley cranked a two-run, walk-off homer in the 13th inning to send the Astros to their biggest comeback victory in more than 25 years, beating the Mariners, 11-9, in 13 innings on Thursday night at Minute Maid Park.

• Box score

“That’s what makes this team special, a never-give-up attitude and we’re always in every game,” Brantley said.

The Astros improved to 13-1 this season against the Mariners, beating them for the eighth time in a row, while seeing their magic number to clinch the American League West reduced to 14. It was Houston’s biggest come-from-behind win since wiping out an 11-0 deficit to beat the Cardinals, 15-12, on July 18, 1994.

“A lot happened in the game and obviously started out terribly for us but finished in dramatic fashion,” Astros manager AJ Hinch said.

Miley, who entered Thursday with the third-best ERA in the American League, failed to retire any of the six batters he faced and was rocked for a season-high five runs. He became the first Astros pitcher since Jim Clancy on Aug. 3, 1989, to not record an out without being injured or ejected.

“It’s the best I felt in a month,” Miley said. “They had me today. Tip your hat. Sometimes you get your butt whipped and I got my butt whipped.”

Here’s how the Astros pieced together a comeback:

Starting from scratch

Trailing 7-0, cleanup hitter Yordan Alvarez reached on an error to start the second inning and scored on a wild pitch to get the Astros on the board. All-Star third baseman Alex Bregman gave the Astros life when he ripped a two-run double in the third inning, scoring Josh Reddick and José Altuve. For the season, Bregman has 98 RBIs, which is five shy of his career high set last year.

“They had seven runs before our cleanup hitter got to hit for the first time, so you have to stay in the game,” Hinch said. “We just hung in there and kept chipping away and got some big swings and look up and we tied the game.”

Mariners 7, Astros 3

Tucker, Reddick hit big homers

Kyle Tucker, the Astros’ top position-player prospect who’s starting in place of the injured George Springer, led off the sixth with his first career homer. One out later, Reddick hit his first homer since June 28, snapping a 172-at-bat drought, to make a game out of it. Reddick went 3-for-3 with three runs scored.

“That was pretty surreal,” Tucker said. “The whole crowd cheering and getting back in the dugout and everyone is super happy. That was awesome.”

Mariners 7, Astros 5

Altuve delivers

After Austin Nola hit his second homer, a solo shot in the seventh, Altuve followed a hit-by-pitch to Robinson Chirinos and a walk to Reddick with a two-run triple in the eighth, and then scored the game-tying run on a Brantley sac fly to left field.

“Being down early and the job the bullpen did, the job the lineup did to get us back in the game, it’s a team effort all the way around,” Brantley said.

Mariners 8, Astros 8

Tucker drives in Straw

In the 12th, the Astros answered a second homer by Kyle Seager with a two-out RBI single by Tucker to score speedy pinch-runner Myles Straw from second base to tie the game again. Straw ran for Yuli Gurriel, who had walked.

“Another homer would be great, but you get a single right there and Straw can score,” Tucker said. “He’s fast enough to score on pretty much everything.”

Mariners 9, Astros 9

Brantley wins it

Brantley, who broke an 0-for-17 funk with a sixth-inning single, hit the first pitch he saw from reliever Matt Wisler in the 13th and sent it into the right-field seats to score Jake Marisnick for a two-run homer. It was his third career walk-off homer and career-high-tying 20th homer.

“Any win is a good win, especially this time of year,” Hinch said. “Everybody is scoreboard watching, everybody is paying attention to what other teams are doing. It’s a big win and it feels bigger because the month we’re in and the countdown that we’re having.”

Astros 11, Mariners 9