Pete Alonso is the kind of rookie hitter that Tom Seaver and Dwight Gooden were once rookie pitchers for the Mets. Everybody knows by now that Alonso was no sure thing to even start the season with the Mets when Spring Training began. Now he could hit 50 home runs as a Mets rookie the way Aaron Judge did that for the Yankees two years ago. He is going to knock in 120 runs, or more. Say it again: He isn’t going to win the MVP Award for the National League because Cody Bellinger will -- especially now that Christian Yelich is done for the season. But Alonso has been every bit as valuable to his team as Bellinger and Yelich have been to theirs.

Alonso has lifted the Mets with home runs the way Mike Piazza did when he came to the Mets two decades ago from the Marlins. Piazza finally carried his Mets all the way to the 2000 World Series against the Yankees. At the time Piazza’s manager, Bobby Valentine, told me this about his Hall of Fame catcher:

“When your best player is also a good guy, it filters all the way down through the other 24 guys.”

Once, it was Piazza hitting a home run at old Shea against the Braves when baseball returned 18 years ago, in the shadow of Sept. 11, 2001 -- not just making the city of New York cheer, but making the country cheer that night. It was, and is, the most memorable swing of Piazza’s career. All this time later, on this Sept. 11, Alonso had special patriotic baseball shoes made for all his teammates. The Mets wore them against the D-backs on Wednesday night, 9/11 of this year. And they scored nine runs in the game. And they had 11 hits.

“I just want to give back, and I want to help,” Alonso said on Wednesday night. “I don’t just want to be known as a good baseball player. Hopefully, I want to be known as a good person, too.”

The remarkable rookie season for the kid from Plant High School in Tampa, Fla., continues. In a year when Major League Baseball breaks its all-time home run record, the kid from Tampa leads Mike Trout in home runs and leads Bellinger in home runs and was leading Yelich before Yelich fouled a ball off his kneecap the other night, ending the season of the reigning NL MVP. Alonso won $1,000,000 for winning the Home Run Derby at the All-Star Game in July. Out of that, by the way, he donated $50,000 to the Wounded Warriors Project and another $50,000 to the Tunnels to Towers Foundation, which benefits the families of 9/11 first responders. He has taken to his responsibilities as a star player and the kind of stage he has in New York the way a veteran would. Yeah. Good person. And has put his name -- even his nickname, Polar Bear -- up in lights in the big city.

So here is the question posed to him on Wednesday, as the Mets won a third straight game against the D-backs and kept themselves just two games away from the second NL Wild Card spot:

What were his expectations once he found out he was coming north from Port St. Lucie, Fla., with the big club?

“If you told me before in my rookie season that we were going to be in a playoff race, and then I’d have this individual success, it would have been kind of a pinch-me thing,” Alonso said. “Like, really? That’s what I’m walking into my first year? Really? Seriously? I mean this year so far has just been unbelievable.”

Seriously? It has been unbelievable. With the last chapter, for him and his team, yet to be written. Alonso and the Mets were counted out at the All-Star break. They were counted out again after the Cubs swept them not long ago at Citi Field. They were counted out when the Nationals scored seven runs one night in the bottom of the ninth to beat the Mets, 11-10. And here they are. There are a lot of reasons why the Mets somehow keep coming. But there is no way they are not in play without Alonso, who has become one of the great home stories in the history of baseball in New York. This is what he’s done in his first year? Really? He has changed everything at Citi Field.

Alonso’s high school coach, Dennis Braun, told me last month to call him when Alonso got to 50 home runs. I fully expect to be calling Coach Braun by the end of next week. He told me when we spoke last that Alonso had the greatest “oppo” -- opposite field -- power he’d ever seen from a high school player. In all ways now, Alonso has power to all fields, all over baseball.

Darryl Strawberry once held the Mets rookie home run record with 26. Unless Alonso gets hurt, he will probably hit twice that this season. The whole season turned out to be a Home Run Derby for the kid from Tampa.