Christian Walker hit a game-winning, two-run homer in the ninth inning to lift the Houston Astros to a 5-3 win over the Seattle Mariners on Sunday.

The game was tied at 3 when Jose Altuve singled with no outs in the ninth. Walker, who had three hits, then sent a fastball from Casey Legumina (4-2) into the seats in left field to give the Astros the walkoff victory and 3-1 series win over the AL West leaders.

Walker's big game came after the struggling first baseman had just three hits combined in his previous seven games.

Bryan King (3-0) struck out Randy Arozarena to end Seattle’s ninth and manager Dan Wilson was ejected for the first time in his career for arguing with home plate umpire Laz Diaz after the call.

Seattle had runners on first and third with one out in the eighth when Ben Williamson hit a grounder to second baseman Mauricio Dubón. He threw home in time to get J.P. Crawford out at the plate before Leo Rivas grounded out for the third out.

The Astros loaded the bases with two outs in the eighth, but Isaac Paredes grounded out to leave everyone stranded. That came after they loaded the bases with one out in the seventh, but came away empty after Seattle turned a double play.

Jake Meyers was on first with two outs in the sixth when Cam Smith laced an RBI double down the right field line to tie it at 3.

Seattle starter Luis Castillo allowed nine hits and three runs with six strikeouts in six innings. Castillo threw 114 pitches Sunday to tie Cincinnati’s Hunter Greene for most pitches thrown in a game this season.

Houston’s Colton Gordon allowed seven hits and three runs in five innings in his third major league start.

Julio Rodríguez had three hits and Mitch Garver drove in two runs for the Mariners.

Rodríguez and Arozarena hit consecutive singles with two outs in the first before Garver made it 2-0 on his double to center.

There were two outs in the third with Rodríguez on third when Donovan Solano singled on a grounder to left field to extend the lead to 3-0.

Houston cut it to 3-1 on an RBI single by Walker with one out in the bottom of the third. A sacrifice fly by Caratini that Leody Taveras jumped to catch on the warning track scored Altuve to make it 3-2.

Key moment

Walker's walkoff home run gave him three RBIs, tying a season high.

Key stat

The teams combined to go 4 for 22 with runners in scoring position.

Up next

Both teams are off Monday before Houston opens a series with the Athletics and Seattle gets a visit from Washington on Tuesday night.