Golden State Warriors shooting guard Klay Thompson has suffered a setback in his return from an ACL injury, according to multiple reports. Per Chris Haynes of Yahoo Sports, the team fears Thompson has suffered a “significant” injury to his Achilles tendon.

Thompson will undergo an MRI on Thursday, Haynes added.

According to Adrian Wojnarowski of ESPN, Thompson suffered a lower right leg injury during a workout in Southern California on Wednesday. As Woj noted, Thompson’s ACL injury was on his left knee.

Thompson was unable to place weight on the injured leg, according to Shams Charania of The Athletic. “Everyone is hoping for the best,” Charania wrote.

Thompson missed all of last season following the ACL injury, suffered during the Warriors’ loss to the Toronto Raptors in the 2019 NBA Finals.

The Warriors were also without point guard Steph Curry for much of last season and finished with the NBA’s worst record.