In the two years since the Mets traded for Yoenis Cespedes,

Terry Collins never has seen his standout slugger mired in a slump like this.

The 31-year-old outfielder was hitting .186 with no home runs and just one double in his last 14 games, before going 1-for-4 with a strikeout in a 5-0 loss to the Cardinals Tuesday night.

The 2017 season simply has not been kind to Cespedes, who signed a four-year, $110-million deal in the offseason. It’s not just this recent stretch. The two-time All-Star has slashed .272/.326/.485 with nine home runs in 46 games.

“There’s a little concern there,” Collins said, “but we also know that when he gets back to what we expect or what we’ve seen, he’s dangerous.”

What Collins and the Mets have seen is one of the most feared hitters in baseball. In his first 189 games with the Mets before this year, Cespedes belted 48 home runs.

It would be logical to assume a slew of lower-body injuries have hampered Cespedes. Hamstring and quadriceps injuries kept Cespedes on the disabled list from late April to June 10. He also sat June 14 with a sore heel, July 4-6 with a hamstring issue and Sunday after tweaking his hip, which seemed to slow him down

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Last night two catchable balls hit to Cespedes in leftfield fell for hits.

“Power’s huge from the legs,” Collins said. “I would have to say just looking at the swings, the lower half seems to be fine. He’s just not getting the bat out in front. He’s getting beat to balls in, and I don’t know if that has anything to do with the lower half because I think that’s still intact. But I can’t say it isn’t.”

Despite Cespedes’ struggles, the Mets’ offense has not been terrible all year. The club was tied for second in the National League with 138 home runs and sixth with 436 runs scored before Tuesday’s games.

At this point, the Mets are so far out of the playoff hunt that even a hot Cespedes might not be much help. They entered Tuesday trailing the Nationals by 14 games in the NL East and the Rockies by 10 ½ games for the second wild card.

But they certainly would take any production they can get from Cespedes.

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“This is all new to us because this guy has not struggled since he’s been here,” Collins said, “so we’ve got things we’ve got to work on.”