CINCINNATI -- In the middle of the summer, the Mets’ loss on Saturday would be in baseball axiom, a “Hang with ’em.” But this is September, and with every victory precious for the Mets to keep alive their postseason hopes, every moment is magnified, and so is every mistake.

With the bases loaded in the first inning on Saturday, Mets third baseman Todd Frazier assumed for an instant that Aristides Aquino’s ground ball was foul. It was an instant too long, Aquino reached on an infield hit, and a run scored in a game the Mets eventually lost to the Reds, 3-2, at Great American Ball Park.

• Box score

“I made a bonehead mistake,” said Frazier, who also committed a fielding error in the first. “I hesitated for a second. Probably could have had the guy at home. It’s something that cost us one or maybe even two runs. You don’t think. You have to assume it’s a fair ball and play it out from there.”

The Mets are still alive in the National League Wild Card race, but this one hurt. They now trail Milwaukee by 4 1/2 games for the second Wild Card after the Brewers defeated Pittsburgh on Saturday night.

“The way we lost hurts,” Mets manager Mickey Callaway said. “We had multiple chances. Couple of mistakes in the field. We have very few games left. You come here every day to get after it. You have to keep on doing that.”

Christian Colón’s pinch-hit single off Seth Lugo drove in the go-ahead run for Cincinnati in the bottom of the eighth to snap the Mets’ three-game winning streak.

A one-out walk issued to José Iglesias by Justin Wilson helped set up Colón’s game-winner, his first RBI since 2016.

“Walks score,” Callaway said. “That’s why you want to limit those walks, because then they can get lucky after and some damage can happen.”

Following the two-run first inning, Mets starter Zack Wheeler finished strong, allowing only four hits over the next five innings.

The Mets loaded the bases in the fifth after Reds first baseman Joey Votto’s throwing error on Wheeler’s sacrifice bunt attempt. Reds starter Anthony DeSclafani then hit Brandon Nimmo to force in a run, tying the score at 2.

Back-to-back strikeouts by DeSclafani including first baseman Pete Alonso for the final out left the bases loaded.

Alonso went 0-for-4 with a strikeout to remain two home runs shy of Aaron Judge’s all-time rookie record of 52.

Wheeler worked around a leadoff double by Votto in the fifth to keep the score tied. It was the third straight start that Wheeler has allowed one earned run over seven innings. The last two outings have resulted in no-decisions, as did Saturday’s.

“Today hurts, just have to pick it right back up and win the series tomorrow,” Wheeler said. “Any time of the season, but this time in particular, you just have to bear down and make your pitches. That’s what I’m trying to do.”

The Mets managed only three hits off DeSclafani who owns a 2.05 ERA over his past seven starts, and they couldn’t muster any offense off the Reds’ bullpen either.

Cincinnati won despite playing short-handed with outfielder Josh VanMeter, infielder Freddy Glavis, and relievers Michael Lorenzen, Robert Stephenson, Kevin Gausman and Keury Mella out with flu-like symptoms.

Reds pitchers retired the final 14 Mets batters to close out the victory, including three straight strikeouts in the ninth by closer Raisel Iglesias.

“It’s a tough one,” Frazier said. “These are the games you’re supposed to win. I felt like we had to go 9-1 [down the stretch]. Here’s our one. We let it get away. When you lose, you have to hope for some losses. That’s the stage we’re at right now and that’s not a good stage.”