KANSAS CITY -- Pete Alonso took a powerful swing, and the loud crack of the bat told the story. The towering drive cleared the left-field wall at Kauffman Stadium with ease, and the Mets' slugger suddenly had his 40th homer, a new single-season record for a National League rookie.

Alonso's ninth-inning blast in the Mets' 11-5 win over the Royals on Sunday moved him past the Dodgers' Cody Bellinger for the NL rookie record. With 38 games remaining, Alonso trails only Aaron Judge (52 homers) and Mark McGwire (49) on the all-time rookie list.

"It's crazy," Alonso said. "Coming into camp, I didn't even know if I was going to make the team or not. To break this record and have a good season, it has been unbelievable."

The home run ball ended up in the hands of a Royals fan, who was gracious in making sure it was returned to Alonso. The Mets' first baseman reciprocated by providing an array of souvenir items in exchange for the ball.

Alonso's 40th homer, which came against Royals reliever Jacob Barnes, leaves him only one shy of the Mets' single-season record. Todd Hundley hit 41 homers in 1996, and Carlos Beltran matched that mark in 2006.

"There have been so many Mets greats," Alonso said. "It's hard to believe I am one away from tying that. That's even more mind-boggling. I'm just really grateful and thankful that I've had this opportunity."

Mets manager Mickey Callaway appreciates the work ethic that Alonso has displayed in the rookie's record-setting season.

"A lot of hard work and dedication," Callaway said. "You have to be so proud for a kid like that."