Golden State Warriors guard Klay Thompson suffered a torn right Achilles’ tendon that will end his 2020-21 season before it started.

Thompson, who missed the entire 2019-20 season after tearing the ACL in his left knee during the 2019 NBA Finals, was working out in Los Angeles when he was injured Wednesday. The diagnosis was confirmed during an MRI exam Thursday, the team announced.

Along with Stephen Curry and Draymond Green, Thompson is a part of Golden State’s homegrown core that won three championships and advanced to five straight Finals from 2015 to 2019. The five-time all-star guard averaged 21.5 points, 3.8 rebounds and 2.4 assists per game during the 2018-19 season and shot better than 40 percent on three-pointers for the eighth straight year.

The injury is a devastating blow to Thompson, who had spent the past 17 months recovering from his knee injury, and to the Warriors, who had hoped to return to title contention after plummeting to the West’s worst record in 2019-20. Golden State General Manager Bob Myers looked shaken while addressing the media Wednesday night after selecting Memphis center James Wiseman with the second overall pick.

“It was hard to disengage mentally from [Thompson’s injury], but we had a lot of stuff going on as far as drafts and trades,” Myers said. “I couldn’t really let my mind go all the way there.”

Without Thompson, the Warriors find themselves at a crossroads with free agency opening Friday. Ownership and the front office must decide whether to invest in this season knowing that trying to compete will be significantly more difficult without Thompson or pivot toward a rebuilding approach.

The fundamental question the Warriors need to ask: Do they believe Curry, Thompson and Green, who are all 30 or older, will still be able to lead a title team in 2021 and beyond? Golden State has committed significant resources to its three core stars. Curry signed a five-year, $200 million contract in 2017, Thompson a five-year, $189 million deal in 2019 and Green a four-year, $100 million contract in 2019.

In the short term, the Warriors moved quickly to line up a replacement for Thompson by agreeing to a trade with the Oklahoma City Thunder for Kelly Oubre, according to ESPN. The 24-year-old forward, who averaged 18.7 points and 6.4 rebounds per game for the Phoenix Suns last season, is a capable starter, but he can’t replicate Thompson’s elite shooting and on-ball defense.

Oubre will earn $14.4 million in the final year of his contract, but the Warriors’ luxury tax bill will balloon upon his arrival. According to one estimate, Golden State’s tax bill would rise from $66 million to $134 after adding Oubre, although the Warriors and all other taxpaying teams will get a partial refund on their tax bills that is proportional to the NBA’s revenue decline during the upcoming season due to the coronavirus pandemic.