Mets first baseman Pete Alonso acknowledges fans as he comes...

Mets first baseman Pete Alonso acknowledges fans as he comes out of the game at the top of the 11th inning against the Braves at Citi Field on Sunday. Credit: Kathleen Malone-Van Dyke

Without hitting another homer or playing another game, Pete Alonso added another bullet point Monday to his list of accomplishments: National League Rookie of the Month for September.

Alonso, a virtual certainty to be named NL Rookie of the Year on Nov. 11, won the monthly rookie honors three out of six months this season. That matched the number of those awards won by Mets rookies in the previous seven years.

Alonso, 24, hit 11 home runs in September — his most in any month — and had 19 RBIs and a .245/.322/.585 slash line. The strong finish brought his homer total to 53, the most of anyone in baseball this year and the most of any rookie ever, and his RBI total to 120, tied for third-most in Mets history.

No Mets player has hit more homers in a season. The only Mets to drive in more runs are Mike Piazza (124 in 1999) and David Wright (124 in 2008).

And you can be sure Alonso found satisfaction in his season. On Monday on Instagram, he posted a screenshot of a “scout’s take” from Baseball America, a respected prospect ranker, from spring training. In it, the unnamed scout said Alonso “isn’t any better” and is “still stiff” defensively.

“Right now, he’s taking advantage of the fastball,” the scout said. “I can’t recall him ever hitting a slider. I’m not confident that Pete Alonso has the skills to be a hitter.”

Against sliders this year, Alonso hit .263 and slugged .474 with five homers, according to Brooks Baseball.

And he wrote, in part: “Here’s a lesson: self-belief and determination is more powerful than what ‘experts’ think.”

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