Thompson was looking to return this season after missing all of last year with an ACL injury.
Warriors All-Star guard Klay Thompson suffered an Achilles tear on Wednesday, according to ESPN's Adrian Wojnarowski.
He will reportedly miss the entirety of the 2020–21 NBA season.
The Warriors announced Wednesday that Thompson suffered a lower right leg injury in a workout and was undergoing tests to determine the severity of the injury. He underwent further imaging on Thursday.
The injury occurred during a workout in Southern California with other NBA players present. Thompson was unable to place weight on his lower right leg while leaving the gym, according to The Athletic's Shams Charania.
Thompson, 30, was looking to return this season after sustaining a left ACL tear during Game 6 of the 2019 NBA finals. He missed all of last season rehabbing the injury.
The Warriors guard was fully cleared to train without restriction in mid-June, nearly one year after he suffered the injury against the Raptors.
He agreed to a five-year, $190 million deal to stay with the Warriors at the start of last summer's free agency. Thompson averaged 21.5 points per game in 2018–19 while shooting 46.7% from the field and 40.2% from three. He has made the All-Star team in each of his last five seasons.
Warriors general manager Bob Myers said Wednesday evening he did not know the extent of Thompson's injury, just that he's "hoping for the best."
The Warriors went 15-50 last season and selected center James Wiseman with the No. 2 pick in Wednesday's draft.
Myers said Golden State's decision to select Wiseman was not impacted by Thompson's injury.
“We had him No. 1 on our board when all the dust settled," Myers said of Wiseman. "Certainly the Klay thing made you think for a second, but it was just a short amount of time and we decided we're staying the course of what we always felt but you have to take pause and think about things for a second."