KANSAS CITY -- The Mariners hit four home runs, including two by designated hitter Nelson Cruz, to propel themselves to an 8-7 win over the Royals in the first game of a doubleheader on Sunday afternoon at Kauffman Stadium.

With the win, the Mariners drew within a half-game of the Royals and Rays, who are tied for the second American League Wild Card spot. Kansas City remained three games behind the Indians in the AL Central after Cleveland lost to the Yankees.

The Mariners pounced on Royals left-hander Danny Duffy early, as first baseman Danny Valencia hit a two-run home run in the first inning. Third baseman Kyle Seager followed with his 16th home run three batters later.

Cruz hit his first home run of the day, a three-run shot that gave the Mariners a 7-0 lead, in the second inning. In the seventh, Cruz hit his second homer of the game, a 465-foot blast, according to Statcast™, that became the Mariners' longest home run this season.

"Cruz really swung the bat well," said Mariners manager Scott Servais, who had the big designated hitter back after he missed Friday's game with back spasms. "A couple of those balls he hit were unbelievable. That second one was just a bomb. And we needed it. We needed every run today."

Mike Moustakas hit a two-run home run, his 31st of the season, off right-hander Nick Vincent in the eighth inning to cut the Royals' deficit to one run, but Vincent didn't allow another run, and Edwin Diaz recorded his 23rd save.

"The one tack-on home run, the one that Cruz hit, ended up breaking our back right there," Royals manager Ned Yost said.

Rookie Marco Gonzales allowed seven hits and five runs in four-plus innings in his Mariners debut in place of Felix Hernandez, who went on the disabled list Saturday with biceps tendinitis. Gonzales was acquired two weeks ago from the Cardinals.

"That was beautiful," Gonzales said of being spotted a seven-run lead by his offense. "That was amazing. I was thanking everybody in the dugout. That was so great. It's so nice to pitch with the lead right away. It calmed the nerves a lot and I just tried to go out and fill up the strike zone."