According to Rapoport, Fountain will likely have surgery right away. ESPN's Tony Grossi reported practice was immediately halted after Fountain was injured. CBS Sports Bryan DeArdo noted Colts coach Frank Reich and owner Jim Irsay spoke to Fountain as he was being carted off the field, and several Browns players showed support.
Fountain was a fifth-round pick in the 2018 NFL draft and led the Colts in receiving in last week's preseason win over the Bills.
The Browns and Colts face off Saturday in a preseason contest.