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Clay Holmes looks like he’s run out of gas.

Unfortunately for the Mets, they still have a ton of road left to go.

Another poor outing by Holmes threatened to ruin Pete Alonso’s big night, as Holmes failed to get out of the fourth for a no-decision in a 13-5 Mets win over Atlanta.

After Alonso hit his franchise record 253rd homer, Holmes gave back a 5-1 lead by coughing up four runs in the fourth, with the bottom of the order doing much of the damage.

“He had a hard time landing the sinker for strikes. He was missing arm-side a lot,” said Carlos Mendoza. “We could’ve done a better job recognizing that he was missing arm-side, maybe start using the cutter, some of the other pitches.”

Holmes allowed six hits, five earned runs and walked five in just 3 ²/₃ innings.

With Frankie Montas already out of the rotation, Mendoza doesn’t appear set to do the same with Holmes.

“When you have a night like [this], you’re always going to start questioning. But he’s coming off an outing with five innings, 75-pitch efficiency,” Mendoza said. “He keeps saying he’s fine, the sinker is 96 [mph], the movement. He just had a hard time throwing that pitch for strikes. So we’ll continue to check on him, continue to make sure we’re not missing anything. He’s a big part of this team.”

With Nolan McLean and Brandon Sproat waiting in the wings, Holmes trudged of the mound to boos from 39,748. He’s struggled to a 5.10 ERA with 27 walks and 33 strikeouts over his past 10 starts.

A reliever throughout his career before this season, Holmes had never thrown more than 70 innings and is now up to 126, even after failing to get out of the fourth for the second time in three starts.

But he cited pitch selection, not fatigue.

“The sinker had been working. I got a couple of ground balls and in those situations, you just have to keep trusting it. I started getting a little too fine and then had to go over the plate in counts where I probably shouldn’t have,” said Holmes. “Looking back, I just had to keep going, and if they want to hit five singles in a row, do it. But I can’t put myself in bad counts, and it really helped them out.

“Overall the sinker has been pretty good, just attacking and trusting early. When I’m in good counts with it, I’ve had pretty good results. I feel like the same thing, when I help them out and put some walks on, it fuels some momentum and the singles score runs versus just maybe a run or a guy get on base. So when I’m in good counts, I feel like I’ve been pretty good. It’s just stay on the attack for me.”