Aristides Aquino broke the National League rookie mark for homers in a month on Thursday with his 14th in August.
Cody Bellinger had the previous mark with 13 home runs in June 2017. The Major League record for a rookie is 18 by the Detroit Tigers' Rudy York in August 1937.
"Speechless," David Bell said. "Guys are having fun watching him and what he's doing. Pretty special."
Aquino was promoted on Aug. 1. He tied the Reds record for homers by a player in a month held by Frank Robinson (1962) and Greg Vaughn (1999). He leads majors with 32 RBIs this month.