HOUSTON -- Given the extent of their offensive struggles during their season-opening homestand, the Houston Astros were in need of something unexpected to break out of their collective funk and salvage the finale of their lost weekend series.

After Jake Marisnick, a defensive substitution in the eighth inning, sent the contest into extras with his solo home run in the ninth, Evan Gattis turned his career-high third walk of the afternoon into a walk-off winner in the Astros' 5-4 victory over the Kansas City Royals on Sunday at Minute Maid Park.

Gattis followed a leadoff infield single by George Springer in the 12th inning and walks to Jose Altuve (intentional) and Brian McCann. Royals left-hander Matt Strahm (0-2) sailed his 3-2 pitch to Gattis high to force home Springer.

Gattis finished 2-for-3 with three walks and a run, and was one of four Astros with multi-hit games (Springer, Altuve and shortstop Carlos Correa).

Marisnick homered off Royals closer Kelvin Herrera with one out in the ninth, a laser down the third-base line that ricocheted off the top of the left-field wall. For Marisnick, his second hit this season was the Astros' third home run of the game.

"It's a good reminder that we're going to need contributions from an entire roster," Astros manager A.J. Hinch said. "We're going to need a little bit of all of this to get where we want to get."

The Royals (2-4) first coughed up a two-run lead in the seventh when Astros first baseman Marwin Gonzalez golfed his third homer into the Crawford Boxes in left, doing so against left-hander Travis Wood and driving home Gattis in the process.

"We were kind of unlucky the whole game," Royals manager Ned Yost said. "Both home runs that they hit late wouldn't have been home runs in any other park in baseball, but unfortunately, we were playing in this park. A few things didn't bounce our way today."

But Brandon Moss helped the Royals reclaim a 4-3 lead with his first homer off Astros right-hander Chris Devenski (1-0) in the top of the ninth. Moss followed dingers by Salvador Perez in the second inning and Mike Moustakas in the sixth.

Perez and Moustakas homered off Astros right-hander Lance McCullers, who allowed three runs on six hits with 10 strikeouts over seven strong innings.

Devenski had seven strikeouts in four innings of relief for Houston (4-3). It marked his second outing of four innings with seven strikeouts this homestand.

"I try to study as much scouting reports as I can on as many hitters," Devenski said. "It is tough, but it's something that I like to do. If I can help the team win, so be it.

"We got the 'W' and we found a way. We didn't give up and continued to push. It was big -- that (Gattis) walk was cool."

Making his first road start since June 20, 2016, with the Seattle Mariners, Royals right-hander Nate Karns produced a strong effort. He surrendered a leadoff homer to Springer in the bottom of the first but was unscathed after that.

When Karns departed with two outs in the sixth, he led 2-1. But his bullpen proved unable to build on his outing, surrendering the lead not once but twice.

"I thought he did a great job," Yost said. "First two innings were a little erratic, gritty, but he settled down in the third and pitched great from that point on."

NOTES: Astros 2B Jose Altuve recorded his 200th career stolen base with two outs in the eighth inning. Altuve became the seventh Houston player to reach that milestone. ... Royals C Salvador Perez homered in his fourth consecutive game, becoming the first Kansas City player to accomplish the feat since Billy Butler on July 26-29, 2011. ... Astros RHP Lance McCullers has allowed three or fewer runs in each if his 22 starts at Minute Maid Park. The only pitcher in club history with such a streak is RHP Larry Dierker, who did so in 22 consecutive starts in 1970-72. ... Astros DH-LF Carlos Beltran was not in the starting lineup. Houston manager A.J. Hinch plans to rest Beltran, who turns 40 on April 24, on day games after night games. Beltran pinch-hit in the seventh inning and flied out to center field.