Noah Syndergaard stalked off the mound and toward the dugout shaking his head and talking to himself like something had gone horribly wrong. It couldn’t have been further from the truth. The fans at Citi Field reminded him as he reached the first base line with a loud standing ovation. The big righthander stopped musing and touched the bill of his cap to acknowledge their appreciation.

It’s nice the Mets’ lineup broke out of its slump on Wednesday night against the Pirates. It didn’t have to happen right there. Syndergaard had Pittsburgh throttled from the outset and didn’t let up until he finally ran out of gas in the ninth of the 11-2 win.

The only thing he had to be upset about was when manager Terry Collins came to remove him. He hadn’t finished off the complete-game shutout he had going when the inning started. He wanted those firsts badly, but ended up giving up a pair of runs (one unearned).

“Pretty badly. I was not really satisfied with myself after not being able to complete the game,” Syndergaard said. “It was still a lot of fun to be a part of . . . Sometimes I try to focus on too much of the negative because I want to do so well for myself.”

He did well. After giving up a leadoff hit in the first inning to John Jaso, Syndergaard (7-2) retired the next 17 Pirates. He threw a career-high 8.1 innings allowing only five hits, walking none and striking out 11.

It was a nice bounce back after the Pirates scored twice in the first inning off him in Pittsburgh a week earlier.

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“The last time he faced the Pirates, they were on his fastball. He went out to pitch today, he wanted to win the game and he did a great job mixing it up,” Catcher Rene Rivera said. “They were aggressive and he used the breaking ball a lot early in the counts and he got some outs — Curveball, slider and change — all of them were good. You keep the hitters off-balance. You could see it today: they were off-balance.”

The crowd erupted when Syndergaard came to bat with two out in the bottom of the eighth, sensing that this might be a chance to see a complete-game shutout. And when he found trouble in the final inning they showered him with chants of “No-ah! No-ah!”

“He deserved to go out there in the ninth inning and see if he could get the shutout,” manager Terry Collins said, adding that the week off and the extra day of rest he will get before the next start left him confident about sending him back out.

Syndergaard said he didn’t hear the chants during the ninth because “I was too locked in, just tunnel vision out there — it just went silent and tried to finish the night out.”

But he did hear them before he reached the dugout.

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“It’s a great feeling,” he said. “We have the best fans in baseball. They root for you 100 percent of the time. I couldn’t be happier to be a Met.”