Hargreaves had the injury confirmed after getting a second opinion from Dr. James Andrews in Pensacola, Florida.
Hargreaves finished the game with seven combined tackles, a pass breakup and a forced fumble.
After struggling in 2017, Hargreaves sat down with the coaches and was told he needed to make big improvements this offseason. He fought off rookie second-round draft picks Carlton Davis and M.J. Stewart, as well as third-year cornerback Ryan Smith, during training camp to keep his starting job.
The Bucs signed cornerback Marcus Williams on Tuesday to provide some much-needed experience. Free agent Bashaud Breeland was also brought in for a visit, a source told ESPN.
In other moves, the Bucs also re-signed defensive end Will Clarke, who played 15 games for the Bucs last season, and signed tackle Jarron Jones to the practice squad.