Pete Alonso didn't officially make any errors Friday night, but he still faulted himself for a major miscue.

Alonso's Mets took on the Cardinals, whose touted shortstop, Masyn Winn, made his major league debut in the second game of the four-game series in St. Louis.

Winn struck out in his first at bat, then stepped to the plate with two outs in the fifth inning and hit a chopper down the third-base line, beating the throw for his first big league hit. As the crowd cheered the rookie's feat, Alonso corralled the ball, gathered himself and then launched it into the stands at Busch Stadium, potentially depriving Winn of a lifelong memento as those cheers quickly turned into boos.

Alonso fully took the blame after the game, saying he didn't even realize what he did until some former teammates in the Cardinals dugout "were just like, 'Pete, what the hell are you doing?'"

"I was like, 'Oh, God,'" an anguished Alonso told reporters after the Mets' 7-1 win.

"That was a huge mistake. Not a fun one to make. I feel awful about it."

The good news for Alonso -- and Winn -- was that the ball eventually was retrieved and given to the 21-year-old, who was a second-round pick of the Cardinals in the 2020 draft.

"He apologized on first (base), and when he got to second later, he apologized as well," Winn said of Alonso. "Complete accident. I thought it was quite funny. Especially after we got the ball back, I thought it was a little more funny."