Ronny Mauricio will not be the only top prospect joining the Mets when September begins. 

Brett Baty will be recalled and will rejoin the club for Friday’s series opener at Citi Field against the Mariners, a league source confirmed Thursday. 

Baty was demoted in early August as the young third baseman struggled against major league pitching.

He returned to Triple-A Syracuse and posted an .822 OPS in 17 games.

There will not be an 18th. 

Baty will join Mauricio in Queens, where another roster move will have to be made because both are hitters.

As September begins, the Mets can add one position player and one pitcher to an expanded, 28-man roster.