ST. LOUIS — Last season, Fernando Salas helped solidify the Mets’ bullpen, pitching to a 2.08 ERA in 17 appearances after being obtained from the Angels in a trade. This season, he has personified all that has gone wrong with the Mets’ embattled relief corps.

Salas contributed to Saturday’s 4-1 loss to the Cardinals. He left with the bases loaded in the seventh inning after surrendering a run and recording two outs. “It’s baseball. Every season is different,” said Salas, whose ERA rose to 6.44 in 40 appearances. “If there was a secret, I’d tell you.”

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The Mets re-signed Salas to a one-year, $3-million deal during the offseason, but he has been shaky. He has allowed four runs in 2 2⁄3 innings in his last three games and gave up a walk-off hit against the Nationals on Monday.

“He was a guy who could get ahead in the count and be able to move the ball around in the strike zone to get outs,” manager Terry Collins said. “Right now, he’s behind in the count and now he’s got to come into the middle of the plate. That’s just not part of what he does.”

Extra bases

Erik Goeddel has stranded all nine of his inherited runners this season . . . With a three-hit game, T.J. Rivera extended his hitting streak to eight games . . . Travis d’Arnaud continues to show improvement with his throwing. He caught two of four potential base-stealers.