And it didn't get better. Vargas gave up five runs, including three home runs, over six innings in the Royals' 5-3 loss.
Vargas, who missed almost all of last season recovering from Tommy John surgery, is at a loss to explain the turnaround. Vargas said he has felt as a good as ever in his last few starts -- the results just aren't there.
"I felt like I had really good rhythm all game," Vargas said. "I really felt like we should have come out of it better than we did tonight."
Vargas retired the first seven hitters he faced before Adeiny Hechavarria hoisted his fifth home run of the season. The Rays pushed across two more runs that inning.
After the Royals fought back to tie the score on Whit Merrifield's three-run homer, Vargas gave up home runs to Steven Souza Jr. and Logan Morrison in the fifth.
"It's just frustrating because I felt really good," Vargas said. "I felt really good about what we were doing. Tough one to swallow."
Vargas seemed especially baffled that Souza came up in the fifth looking for something offspeed.
"First first-pitch curveball I'd thrown to a right-hander all night," Vargas said. "You don't usually bank on that. Tip your hat. He went up there ready to swing."
Vargas said he doesn't believe he has changed much as a pitcher in the second half.
"You feel you're capable of getting out of situations that put the other team in a good position to win the games," he said. "And we were able to do such a good job of not letting that happen early in the season. So it's the mental battles that you got to overcome.
"Hopefully things turn and we get on a nice roll."
Royals manager Ned Yost understands that fatigue could be a factor for Vargas.
"He went from 12 innings last year to over 150 now," Yost said. "It is up there. It's a pretty big swing. But he keeps going out there and competing."