Half of Jersey Shore's cast is reportedly on the chopping block for the MTV reality series' third season.

Sammi "Sweetheart" Giancola, Vinny Guadagnino, Ronnie Ortiz-Magro and Angelina Pivarnick "under whelmed" MTV executives during filming for Jersey Shore's second season and could be replaced for the third season, TMZ reported Wednesday.

"They should be very worried," a source told TMZ.

Four new members would join Jersey Shore for the third season along with Jenni "JWoww" Farley, Michael "The Situation" Sorrentino, Nicole "Snooki" Polizzi and Paul "Pauly D" DelVecchio -- who would reportedly remain with the cast.

Jersey Shore's second season will premiere Thursday, July 29 at 10PM ET/PT and begin with the cast living in Miami before they return to Seaside Heights, NJ for its conclusion.

All of the show's first-season cast members returned for the second season, including Pivarnick -- who left Jersey Shore's first season after the first few episodes.