Noah Syndergaard believed he had already reached rock bottom.

The imposing Mets pitcher’s E.R.A. was a bloated 6.35 after the season’s first month, and his record was 1-3. He no longer trusted his breaking pitches, and when he stood on the mound, he could not grip the baseball. The ball, he said, felt “slick as can be.”

“Like holding an ice cube,” he said.

But on Thursday at Citi Field, Syndergaard caught fire with a historic all-around performance. In a matinee outing, he offered the 21,445 fans in attendance a one-man show that lasted just over two hours and put him in rarefied territory for major league pitchers.

In addition to striking out 10 batters in a complete-game shutout, Syndergaard rerouted a fastball 407 feet to left field for a solo home run in a 1-0 win over the Cincinnati Reds. It was only the seventh time in major league history that a pitcher homered and threw a 1-0 shutout, and the first time it had been done by a Met. The last pitcher to accomplish the feat was Bob Welch of the Los Angeles Dodgers in 1983.