Charlie Riedel / AP

Craig Stammen figured to be the perfect relief weapon for the Nationals in their series against the Cardinals. All year he pitched multiple innings if a starter needed to be bailed out, and his sinker-curve repertoire could neutralize the Cardinals’ powerful, right-handed lineup.

Instead, Stammen has faltered in all three games. Wednesday, he hit Yadier Molina with a pitch, allowed a double by David Freese and yielded a screaming sacrifice fly. For the series, Stammen has allowed three runs in 2 1/3 innings on four hits and two walks while hitting three batters.

“I’ve been a little off the last couple days,” Stammen said. “So I just got to figure it out here.”

It has not been an accurate representation of Stammen’s outstanding regular season, when he posted a 2.34 ERA in 88 1/3 innings, the most of any pitcher in the Nationals’ bullpen. Even after Stammen struggled in his first two outings, Manager Davey Johnson  turned to him in Wednesday’s Game 3 after Edwin Jackson left.

“That’s his spot,” Johnson said. “He’s a bull. It wasn’t because he was tired.”

Stammen has felt sick, having come down with the same fever Bryce Harper is fighting. But Stammen said the illness has nothing to do with his performance. After reviewing his performance, he picked up a mechanical flaw.

“I watched the tape,” Stammen said. “It looked like I was pushing the ball. The ball was moving left to right rather than down. I’m not sinking the ball, which is what’s made me successful this season.”