Kroft hyperextended his knee during Tuesday's practice, Ian Rapoport of NFL Network reports.
Kroft was filling Tyler Eifert's shoes due to the latter's continued recovery from ankle surgery. After suffering his own injury, though, Kroft could be sidelined for a spell in training camp. While a timetable won't be established until he undergoes an MRI on Wednesday morning, Ryan Hewitt is the next man up in the TE hierarchy in Cincinnati.