Every so often Kansas City's Whit Merrifield will swing at the first pitch of the first inning no matter what just to make sure his scouting report doesn't become predictable.

"That way pitchers don't just groove one every time and you're sitting 0-1 every at-bat," Merrifield said. "It's important as the leadoff guy to get on the first pitch every once in a while."

Merrifield picked the right time, hitting Felix Hernandez's first pitch of the game for his seventh home run as the Kansas City Royals beat the Seattle Mariners 7-3 on Tuesday for their fifth win in six games.

Merrifield set the tone jumping on an 89 mph pitch in the middle of the plate and clearing the wall in left-center. Mike Moustakas continued his home run roll at the plate hitting a two-run shot for his 24th of the season and the Royals knocked around Hernandez (3-3) for five earned runs in six innings. Moustakas has homered five times in the past seven games.

The Royals scored three times in the fourth inning thanks to Moustakas' long ball and a two-out error by second baseman Robinson Cano that allowed Brandon Moss to score. Salvador Perez had a two-run double and the five earned runs were the most allowed by Hernandez in his eight starts this season.

"I was just looking for something out over the plate," Moustakas said. "That guy has been one of the best pitchers in baseball for a long time so I was trying to put a good swing on something early in the count and not get to two strikes."

Kansas City starter Danny Duffy (5-4) returned after spending a month on the disabled list and allowed just two first-inning runs.

Nelson Cruz had a two-run single off the wall in right-center field in the first inning — missing his first home run in a month by a matter of inches — but Duffy allowed just one other runner to reach third base pitching into the sixth. The lefty had been on the DL since late May with an oblique strain, but scattered five hits and struck out four.

"He looked great. The first inning he was getting his tempo and timing ... but after that he really settled down, found his arm slot and did exactly what we needed him to do," Kansas City manager Ned Yost said.

Jean Segura had an RBI single in the seventh to pull within 6-3, helped along by first baseman Eric Hosmer's throwing error that put runners on second and third with just one out. Reliever Peter Moylan got Danny Valencia to ground into a double play to end the threat, started by Merrifield's lunging stop that kept the grounder from sneaking into the outfield.

Seattle has lost six straight at home and averaged just 2.3 runs per game in those losses.

"The Royals have some momentum going and are playing some good ball and we're not. We need to get some momentum going," Seattle manager Scott Servais said.

ROSTER MOVE

The Royals optioned RHP Miguel Almonte to clear a roster spot for Duffy's return. Almonte threw one inning of relief on Saturday against the Twins in his second appearance of the season.

TRAINER'S ROOM

Royals: LHP Matt Strahm will receive a second opinion on his left knee injury on Thursday. Strahm was initially diagnosed as having a torn patellar tendon.

UP NEXT

Royals: Jason Vargas (12-2) was scheduled to go for his AL-leading 13th win before heading off to the All-Star Game. Vargas leads the AL in wins and ERA (2.22) and has won his past seven starts.