ST. PETERSBURG — Royals left-hander Danny Duffy was back in form as he returned from the disabled list on Thursday and tossed five productive innings.

Duffy gave up two runs and six hits, but he worked out of trouble early and struck out seven. However, the Royals suffered a 4-3 walk-off loss to the Rays, when rookie first baseman Ryan O’Hearn made a throwing error to home plate with the bases loaded in the ninth at Tropicana Field. Tampa Bay swept the four-game series.

“I didn’t really have any expectations for this start,” Duffy said. “I just wanted to go out there with plenty in the tank and be efficient. I could have been more efficient. But I did make some pitches when I needed to.”

The Royals were officially eliminated from the American League Central race and the postseason.

The Rays loaded the bases with one out in the ninth inning against reliever Brian Flynn. Jake Bauers led off with a walk on a borderline 3-2 pitch, and C.J. Cron blooped a single to right, moving Bauers to third. After a groundout and an intentional walk, Kevin Kiermaier hit a sharp grounder to O’Hearn, who threw low and in the dirt to Salvador Perez, but the All-Star catcher couldn’t make the scoop.

‘I didn’t want to put [Flynn] in a position where he was trapped having to throw strikes, but it was our best chance of trying to get through that inning,” manager Ned Yost said of the intentional walk that loaded the bases. “I wasn’t going to play the infield back, we were just gonna try to cut the run off at the plate. We ended up getting the ground ball that we needed, just couldn’t complete the play.”

Perez acknowledged he had to make a difficult scoop on O’Hearn’s throw.

“I tried to keep my foot [on the plate] and make the scoop,” Perez said. “It’s a little tough.”

Duffy, using an effective four-seam fastball and curve, struck out the side in the first inning to escape a bases-loaded jam. Duffy was nicked for two runs in the third on four singles — two were of the infield variety — and a sacrifice fly, but he once again worked out of a bases-loaded jam to end the inning.

“Of all my offspeed pitches, I’d say my curveball was my best pitch,” Duffy said.

Duffy has found Tropicana Field agreeable in the past. He set a franchise record with 16 strikeouts here in 2016. The lefty, who had been recovering from shoulder impingement, threw 96 pitches, 54 for strikes.

“The mound here is really well manicured,” Duffy said. “I always feel comfortable pitching here.”

Alex Gordon had two hits, a run scored and an RBI for the Royals. Whit Merrifield had two hits, a run scored and a stolen base, his 28th, which tied him for the AL lead.