Juan Soto of the Mets slides home safely for a run...

Juan Soto of the Mets slides home safely for a run during the fifth inning against the St. Louis Cardinals at Citi Field on Thursday. Credit: Jim McIsaac

What makes these Mets so frustrating is the performance that took place Thursday afternoon at Citi Field, where they showed glimpses of being a legitimate competitor in the wide-open National League wild-card race.

It happens every so often, but not nearly enough to be convincing. Not yet, anyway.

Christian Scott persevered through a bumpy start, the bullpen delivered an airtight finish and the Mets slugged three homers, including Juan Soto’s tiebreaking blast in the seventh inning, to avoid the sweep by knocking off the Cardinals, 5-4.

Trying to attach meaning to these occasional gems has become a futile exercise since late April — right around the time the Mets settled into the 10 games under .500 neighborhood and manager Carlos Mendoza received his first public vote of confidence from president of baseball operations David Stearns.

With Mendoza’s job no longer hanging in the balance and his team careening out of playoff contention, the Mets frequently seem to be operating on autopilot, lacking motivation or a sense of urgency.

That’s never a recipe for any sort of revival, no matter how early in the season it may be.

Why the Mets suddenly looked as if they were trying Thursday after sleep-walking through the first two losses to St. Louis — which outscored them 16-2 in those games — is anybody’s guess.

Bottom line, this series with the Cardinals, the current owner of the top NL wild-card spot, was supposed to be a measuring stick for the Mets, a chance to prove they could claw their way back into the playoff conversation. But swiping Thursday’s finale, by the slim margin of a Soto homer, didn’t come close to accomplishing that. It just allowed the Mets to dodge any further embarrassment, a 24-hour reprieve before Atlanta rolls into Flushing with baseball’s best record.

A visit by their longtime NL East nemesis normally would give the Mets an opportunity to make some noise within the division. Not this time, however, as Atlanta has a 15-game lead on the last-place Mets.

The mission this weekend is to try to build some momentum off Thursday’s respectable effort, maybe propelled by Soto, who was in a 3-for-32 (.093) skid before his fifth-inning double, which set up Jared Young’s tying RBI single.

“I don’t have any answers why we haven’t been more consistent,” Soto said. “But I will say it’s part of baseball. You’re going to have ups and downs. It’s just the way you take the downs is going to determine how you’re going to be at the end of the year.”

Those “downs” have been plentiful in Flushing through the first 2 1⁄2 months, as the Mets have stacked the injured list. Before Thursday’s game, Luis Robert Jr. — who you may remember as the Opening Day centerfielder — made a rare clubhouse appearance to talk about his disc herniation. The update didn’t really provide much of an update, however. Robert is able to do some baseball activity but is nowhere near coming off the injured list, where he’s been since April 27.

“I expect to come back,” Robert said through an interpreter. “Honestly, in the beginning, when I first got hurt, I didn’t think it would take so long. But obviously it’s a new injury, and as the days went on, it started getting worse.”

The Mets have found a younger, healthier replacement in the energetic A.J. Ewing, who doubled on Thursday and has reached base safely in eight straight games (10-for-28 in that span). Fellow rookie Carson Benge led off the game with a single that set up Bo Bichette’s two-run homer and Young — who recently returned from the IL — also went deep in the first inning to give the Mets a 3-1 lead.

The Mets collected 10 hits Thursday after managing only eight total in the two losses and improved to 15-5 in multiple-homer games this season. Life gets a lot easier when the ball goes over the fence, and the Mets have been one of MLB’s worst offensive teams all year.

“It’s just good to see it,” Mendoza said. “When we’re going well, you see the conviction when we’re making swing decisions, the way the barrels come into the hitting zone. Right away, you saw it. I think you just set the tone for the whole team like that when you’re able to get out of the gate and put pressure on the other pitcher.”

Even on the rare day Scott was unable to keep the opposing hitters in the ballpark — he allowed three homers in two innings after giving up one in his previous 30 — the bullpen made sure to position the Mets for the win.

When Mendoza went to his four high-leverage relievers, they combined for 4 1⁄3 scoreless innings, and Devin Williams struck out two in the ninth for his ninth save. It was the type of bullpen deployment you’d expect from a contending team, even if the Mets are not deserving of that distinction yet.

So why was Thursday such an outlier?

“I think if we had that answer,” Luke Weaver said, “we would hopefully have more success than we’ve had.”

The Mets (30-38) are still stuck with too many questions. If Mendoza & Co. don’t continue to elevate their play against Atlanta this weekend, the pivotal series could provide the sort of answers they might not want to hear.

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