ST. PETERSBURG — Not even three home runs from the offense and six solid innings from starter Brad Keller could get the Royals back in the win column on Monday at Tropicana Field.

Keller carried a 3-2 lead into the seventh inning when suddenly his slider and four-seam fastball began catching too much of the plate. The result was a three-run outburst by the Rays, who went on to win 6-3 as the Royals’ losing streak reached four games.

“He was limiting his mistakes the first six innings and his pitch count (85) was in great shape,” Royals manager Ned Yost said. “I thought he could go seven or eight innings with the lead.”

But Avisaíl García ripped a double off a hanging slider into the left-center field gap leading off the bottom of the seventh. Garcia advanced to third on a broken-bat infield hit and scored on a fielder’s choice.

Then catcher Mike Zunino ripped a 1-2 fastball that was up from Keller over the center-field fence and the Rays led 5-3.

“Keller made a mistake to Garcia on the double,” Yost said. “Then he gives up that little infield single and I still think he can get out of it with a strikeout and a double play. We just couldn’t do it.

“Tried to go down and away to Zunino and it was kind of up and away. Zunino did a good job of powering it out.”

Keller believed early on that his command was as good as it has been all season.

“I felt really good for the first six innings,” Keller said. “I mean, I felt good going out there in the seventh inning. You know, it was a leadoff first-pitch double and then I made good pitches to the next two guys. Then I just left a ball over the middle of the plate. A guy sees one too many fastballs in an at-bat, he’s going to get it.”

Keller was hurt by the soft contact in that seventh inning, including the broken-bat single from Kevin Kiermaier and a Daniel Robertson grounder that was hit too softly to turn a double play.

“I made good pitches to those two guys,” Keller said. “It’s just unfortunate how they hit it. But, no excuse. I’ve gotta buckle down right there to Zunino and get him.”

Alex Gordon clubbed his fifth home run of the season in the first inning, giving the Royals a 1-0 lead. Gordon pulled a 3-2 sinker from Yonny Chirinos into the right-field seats.

In the fifth inning, Royals right fielder Jorge Soler, who struck out five times Sunday, jumped on Chirinos’ first pitch, a slider, and hit a towering home run into the left-field seats, putting the Royals up 2-1. That was Soler’s sixth home run this season.

“Our offense has been battling,” Yost said. “It’s been battling all season and put us in position to win games.”

Dozier injury update

Red-hot Hunter Dozier clubbed his team-leading seventh home run in the sixth inning, giving the Royals a 3-1 lead. Dozier has been dealing with lower back stiffness and spasms for the past few days and left the game in the eighth, with Lucas Duda pinch hitting for him.

“I felt it before the home run,” Dozier said. “But I had kind of an awkward swing on that single before that and I started to feel it spasm. We tried to get it loose after the home run, but I just couldn’t. It’s been doing this since the first day in New York. Hopefully it will just go away as quickly as it came.”