Thompson suffered a torn Achilles in his right leg while participating in a workout on Wednesday, with an MRI scan confirming the severity of the issue.
The five-time NBA All-Star missed the entire 2019-20 campaign after tearing the anterior cruciate ligament in his left knee during Game 6 of the prior season's NBA Finals.
Now Golden State are once again facing up to an extended period without the 30-year-old, who averages 19.5 points, 3.5 rebounds and 2.3 assists during his eight-year career.
"Golden State Warriors guard Klay Thompson suffered a torn right Achilles tendon, an MRI confirmed today in Los Angeles," a short statement read from the team.
"Thompson suffered the injury yesterday in a workout in Southern California. He is expected to miss the 2020-21 season."
ESPN's Adrian Wojnarowski had first reported the extent of the issue earlier on Thursday, prior to the team's official announcement.
Former Warrior Rick Barry - who was named Finals MVP when they won the title in 1975 - empathised with Thompson on Twitter, as his Hall of Fame career was also hampered by injury problems.
Barry tweeted: "Having had injuries that kept me away from the game I know how devastating it can be emotionally. If anyone can get through this and come back, I’m sure it's Klay with his great work ethic."
Many current NBA players offered prayers for Thompson on social media following the news, among them LeBron James, Luka Doncic and Paul George.
With Thompson's back-court partner Stephen Curry also missing significant time, Golden State finished with an NBA-worst 15-50 record last term.
The Warriors selected James Wiseman with the second pick in the NBA Draft on Wednesday, the center having averaged 19.7 points and 10.7 rebounds in his three-game career at the University of Memphis, as well as guards Nico Mannion and Justinian Jessup in the second round.
The defending NBA champions have endured a difficult up-and-down year, not helped by injuries to Finals MVP Stephen Curry.
But as Curry prepares to return from his latest lay-off, which has so far spanned 11 games, the Warriors are hitting form.
They ended a 5-0 homestand with victory over the New Orleans Pelicans on Friday, improving to 34-30 in fifth place in the Western Conference.
"It's been exciting to see our team, I think, turn a corner," said coach Kerr.
The Warriors are only a game behind the Phoenix Suns in fourth place, giving them a clear target for the remainder of the season.
"You realise how important all these games are from here on out," Klay Thompson added.
"We want to do everything we can to have home court, especially in the first round. So, it's a great challenge, and it's there for us to take."
Thompson, who is scoring 22.1 points per game for the year, has averaged 27.1 points over the last 11 games while Curry has been out and 30.3 points across the Warriors' seven wins in that time.
"Guys have figured out their roles, and I think we are in great condition," he said. "We are having fun, above all."
George Floyd – an African-American man – died in Minneapolis after a police officer was filmed kneeling on his neck during an arrest last week.
Violent protests have broken out across the United States since Floyd's death, during which he was filmed crying out for help as he was handcuffed and pinned to the ground.
Three-time NBA champions Curry and Thompson were among Warriors players to march in the Walking in Unity protest event, along with team-mates Damion Lee and Kevon Looney.
Warriors forward Juan Toscano-Anderson organised the rally and said: "No matter the colour of your skin, how much money you got, your education, it don't matter, we're all human beings.
"We're all here for the same purpose. Not just for black people. Right now it's about black people, but for humanity. There's people all over the world being oppressed.
"And we're just trying to take a step in the right direction and start something – me and my boys, my brothers. Thank you guys for being here."
On Thompson's Instagram story, the five-time All-Star shared footage of the event and wrote: "@juanonjuan10 natural born leader!"
Curry missed 11 games with a shoulder injury but was back in the lineup on Tuesday alongside Andrew Wiggins, who had returned in the Warriors' previous outing after 15 games on the sideline.
However, the Suns defeated the NBA champions 125-113 after building a big halftime lead.
Complacency was an issue, according to Thompson, whose 29 points led Golden State.
"I think with Steph and [Wiggins] back, we probably relaxed a bit more than we should have," he said.
"We thought with them showing up, we'd just get the dub."
The loss was the Warriors' third in a row after a run of five straight wins appeared to have got their season back on track.
At the halfway mark in the campaign, Golden State are eighth in the West with a losing 20-21 record.
"We've been talking about it for a long time," said Curry. "Eventually, you have to do it or else time runs out.
"We have 41 games to figure it out – or else we won't."
There was at least cause for optimism in the fourth quarter, in which Curry, playing with a shooting sleeve on his left arm, scored 16 of his 24 points.
"It's hit or miss with how much rust you will have and how close you can get to the speed of the game," Curry explained. "The first quarter, it felt good just to be out there, running with our guys.
"I felt like I got stronger as the game went on. In the fourth, the intensity of the game picked up. We were playing very desperately trying to come back and make some plays. I felt like myself again."
Coach Steve Kerr added: "I'm hoping that fourth quarter was the team that I have come to know and love and recognise.
"But we have to show in the first quarter, not in the fourth quarter."
The reigning champions, who led by 16 points at one stage, had gone into the final minute with scores tied but Suggs drained a three-pointer, followed by making a steal, sinking one of two free-throws to make it to a two-score game.
Suggs finished the game with 26 points with nine assists, while rookie Pablo Banchero contributed 22 points with eight rebounds.
Curry scored 39 points on eight-of-15 three-point shooting with nine assists for Golden State. Klay Thompson found form with seven triples in his 27-point haul.
The Magic scored 33-of-46 points from the free-throw line, compared to Golden State's 10-of-15.
The result means the Warriors fall to 3-6, having lost three of their past four games to sides who missed last year's playoffs. Golden State are also 0-5 on the road.
Jokic records another triple-double
Two-time MVP Nikola Jokic's third triple double of the season and 79th of his career helped the Denver Nuggets to a 122-110 win over the Oklahoma City Thunder.
Jokic scored 15 points with 13 rebounds and 13 assists as Jamal Murray contributed 24 points including four three-pointers for Denver who improve to 5-3.
For the Thunder, Shai Gilgeous-Alexander scored 37 points but only four in the final quarter when OC went seven-for-22.
Curry, who was injured in the fourth quarter of Golden State's 125-122 loss to the Chicago Bulls on Thursday, is still likely to miss a few games but is not expected to be facing an overly lengthy absence. According to ESPN, the Warriors will have a better idea on the star guard's return timeline as his ankle responds to treatment over the next few days.
Though the Warriors currently reside in ninth place in the Western Conference, their 12-4 record since Feb. 5 is the best among teams in the West and they trail the sixth-place Phoenix Suns by just 3 1/2 games. The top six teams are guaranteed to avoid the play-in round and earn a spot in the conference quarter-finals for the upcoming play-offs.
Curry has stayed mostly healthy this season and is in the midst of another standout campaign, as the 10-time All-Star leads the NBA in 3-point field goals made (290) while averaging a team-leading 26.9 points in 59 games. The Warriors have lost all three games he's missed this season.
The 36-year-old does have a history of issues with his right ankle, however, including two surgeries he underwent in 2011 and 2012.
"I know we're going to miss him if he does have time off,” teammate Klay Thompson said following Thursday's game. “We've been in his position before where he has had time off and we've just got to do it collectively. I know he'll be ready to go when he does come back, whenever that is. We just want to wish him a speedy recovery and to take his time.”
Golden State will play three games in five days beginning with Saturday's home matchup with the San Antonio Spurs. The Warriors then visit San Antonio on Monday before another road game against the Dallas Mavericks on Wednesday.
Thompson suffered an Achilles injury ahead of the 2020-21 season, having torn his anterior cruciate ligament (ACL) in the 2019 NBA Finals, which forced the five-time All-Star sit out the entire 2019-20 campaign.
Reflecting on a tumultuous period as he continues to recover, three-time NBA champion Thompson told reporters on Sunday: "It was probably the worst year of my life, guys.
"It feels good to be back here. I feel love when I'm back in the Warriors facility. My roots are here. [The pandemic] was not easy on anybody. Everyone had their own little trials and tribulations in 2020, but that was it for me -- was losing my grandma Mary, tearing my Achilles, I still think about Kobe every single day.
"There's not a day I don't think about him. And not being able to have that last convo with him... it was a tough year, guys. Not only for me but I'm sure for all of you. I'm looking forward to the future, that's for sure."
Asked about being ready for the start of the 2021-22 season, Thompson replied: "Absolutely. It could be a few weeks after, maybe a month after, but it's definitely going to be geared toward the very beginning of the season."
On the mental challenges following two consecutive season-ending injuries, Thompson added: "It's way harder than any basketball game I've ever had to play. Way harder than any conditioning drill or practice.
"The mental toll is not very fun. You always guess if you're going to be the same player you once were, so you have those natural thoughts, but you can't let those overtake you and you got to realise that this is not unique just to me.
"So many athletes have been through this. Although I was used to playing 100 games a year for the first eight years of my career, this is just a new set of challenges, and with my style of play I feel like could be effective 'til my late 30s, so I'm not going to feel sorry for myself right now.
"I'm just going to keep buckling down and keep doing what I love to do."
Since being drafted by the Warriors with the 11th pick in 2011, the 31-year-old Thompson is averaging 19.5 points, 3.5 rebounds and 2.3 assists per game in his career.
Warriors head coach Steve Kerr confirmed the absence of stars Curry and Green following Golden State's first practice session on Wednesday.
The Warriors have returned to training after their 2019-20 season was cut short amid the coronavirus pandemic – Golden State not qualifying for the Orlando bubble at Walt Disney World Resort with a league-worst 15-50 record.
Curry only made five appearance last season due to a broken left hand sustained in October, while Green was restricted to just 43 games for the injury-hit Warriors.
"First of all, I want to make clear that this is a voluntary camp," Kerr said. "And so [general manager] Bob [Myers] and I have both been in touch with Steph and Draymond and we are well aware of their circumstances.
"And so they both have important family issues to attend to and so they have excused absences."
Kerr added: "Would I like them to be here? Of course. We know, we're watching all these teams in the bubble; the ones that didn't make the playoffs, even they got six weeks together to practice and play games and try different combinations and line-ups.
"And we haven't had that opportunity, so we're just going to use the opportunity that we have here over two weeks, just like the other seven teams that didn't go to the bubble, and we'll try to make the most of this time, get plenty of work in.
"A lot of guys are going to get a lot better and really thrive in this environment. I'm not worried about Steph and Draymond; I know how hard they work and I know they'll be prepared for next season."
Warriors star Klay Thompson is also recovering from an anterior cruciate ligament (ACL) injury suffered during the 2019 NBA Finals.
"He's doing well," Kerr said. "He worked out here at the facility for several days in a row, maybe four or five days in a row with [assistant coach] Chris DeMarco, and Chris gave me really positive updates.
"I was here for a couple of those days and got a chance to see him, and Klay looks great. And he's anxious to play, so we're excited about that."
Thompson has been working his way back to full fitness after sitting out the entire season due to a torn anterior cruciate ligament (ACL) sustained in Game 6 of the 2019 NBA Finals.
Now, the Warriors – who are looking to bounce back after their forgettable 15-50 season – are sweating on Thompson's fitness following his latest setback.
Thompson is believed to have felt pain in his calf during a workout in Los Angeles on Wednesday, with the three-time NBA champion reportedly scheduled to have an MRI on Thursday.
The five-time All-Star has been rehabilitating for more than a year – Thompson took part in his first full practice with the Warriors in September, 470 days following the ACL injury.
Golden State used the second pick to draft center James Wiseman on Wednesday and he was rocked by the news midweek.
"As soon as I seen [the news], it was kind of down for me, like emotionally," Wiseman said. "But the team, we got his back no matter what and he's going to be in great recovery.
"And from my perspective, I just can't wait to go in there and give my great contribution towards the team and just go in there and learn as much as possible.
"Just grow and adapt within that environment and just play my position. But all prayers be to Klay, my team-mate, and he's going to be just fine."
Since being drafted by the Warriors as the 11th pick in 2011, Thompson has a career average of 19.5 points, 3.5 rebounds and 2.3 assists per game.
In 2018-19, Thompson averaged 21.5 points, 3.8 rebounds and 2.4 assists per game as the Warriors eventually fell to the Toronto Raptors in the Finals.
For the first time since Game 6 of the 2019 NBA Finals, the Warriors had their star trio of Curry, Green and Thompson on the court together.
Green had been out since early January due to a back injury, meaning he had been unable to feature since Thompson's return from two serious injury lay-offs.
But the trio were back and as good as ever against the Washington Wizards, who the Warriors defeated 126-112.
Green featured for 20 minutes and had six points, seven rebounds and six assists, while Thompson added 20 points to the Warriors' tally.
Curry, meanwhile, marked his 34th birthday in sensational style, scoring a season-high 47 points and finishing with six rebounds and as many assists.
It was the sixth time in 2021-22 that Curry has enjoyed a 40-plus point game.
"That was magical," Thompson told reporters, while Green enthused: "It was beautiful."
Curry explained: "I think what it did for him is what it did for all of us. You could tell the energy picked up.
"It's not anything more than what's built on 10 years of experience and chemistry and winning and an understanding of how we do things. No matter how much time we have off, we can get right back to it.
"It is crazy to think first time me, Klay and Draymond had been on the court in a very, very long time.
"We want to keep building on that. We know each other like the back of our hand, we complement each other very well."
Golden State have now won four straight games all by double digits, following a five-game losing streak.
The Warriors moved to 47-22 for the season and have now beat every other team in the NBA at least once this season.
Stephen Curry notably played over 30 minutes in the Warriors' road victory, with the recent three-guard lineup of Curry, Thompson and Poole just proving too much.
After only three playoff games in his career, the 22-year-old Poole is leading the Dubs in scoring over the series with 28.7 points per game.
It is not just volume Poole is scoring at but the efficiency, scoring 27 points on nine-of-13 shooting in Thursday's win, with Thompson asserting he is vital to Golden State's NBA title aspirations.
"These three games, I mean, I don't remember a better start for a playoff debut for a guard," Thompson said post-game. "It's incredible what Jordan is doing.
"We need him to go where we want to go, and we need him to keep doing what he's doing.
Opposition defensive schemes effectively have to pick their poison with two the NBA's best three-point shooters ever and Poole, who shot at an astounding 58.8 per cent from the perimeter in the opening two games against Denver.
Thompson is well aware of the spacing Golden State's three-guard lineup provides, but believes it is complemented by Draymond Green and Andrew Wiggins.
"At times, yeah [I feel the space]," Thompson said. "I mean, I had a really good look with like a minute left that I missed – I wish I could get that one back, but that's okay.
"What a fun night at the office. The ball's just flying around, and we played great down the stretch on both sides of the ball. When we move the ball and we trust each other, we'll get open looks.
"We're all great shooters, and Draymond's play-making, and Andrew [Wiggins] is a great shooter as well."
The Warriors beat the Portland Trail Blazers 118-114, but Curry was unable to make any shots from distance.
It ended his record run of 268 games with a successful 3-pointer, as the 35-year-old went 0-for-8 from range. It was the first time he failed to make a 3-pointer in a regulation game since November 8, 2018.
Curry had shot 6-of-8 from 3-point range in a win over the Brooklyn Nets on Saturday, and is the all-time leader in that regard, with 3,505 3-pointers across his career.
But coach Kerr knows the Warriors must not be so reliant on the two-time league MVP.
"We can't rely on Steph to bail us out on every single night," Kerr said.
"It was a tough night for him. But that's what a team is supposed to be about, everybody filling in for each other, different guys stepping up each night.
"That's a great sign, because he's carried us for long enough this year. We need to give him more help."
Curry had just seven points from 31 minutes on the court, but Klay Thompson delivered for the Warriors with 28 points, while Andrew Wiggins contributed 25 from the bench.
Jerami Grant led the game for Portland, with 30 points, while also chipping in with seven rebounds and six assists.
"I feel great, trying to be efficient every night, that’s the goal," Thompson said in an interview with NBC Sports Bay Area.
"Not scoring 50, but just making the most [of chances], taking the shots, and I think I just did well from the last game. Just a great all-round effort."
Careless play put the Warriors down 17 points down at one stage, but they managed to eventually draw level through the shooting of Klay Thompson and Stephen Curry.
Turning the ball over 11 times in the first half, the Dubs started in a sloppy manner against a Denver side fighting to keep their season alive.
The 56-year-old Kerr believes Golden State are still in a good spot and that the nature of the loss can nevertheless act as a good reference point looking ahead in the post-season.
"We needed that," Kerr said post-match. "We took ourselves out of the game because we were too excited, and part of winning playoff basketball games on the road is executing being poised, understanding what's happening and sticking to the game plan. We didn't deserve to win.
"But now, you take that and put it in your back pocket, and you've got it in the memory bank for the next time we're in that situation.
"But the focus now goes to heading home and getting back in front of our fans. This is the situation you want in any playoff series when you're hosting – sweep the first two, get one out of two on the road and go home with a chance to clinch. We're right where we need to be."
Kerr's play-calling down the stretch also came under scrutiny after the loss.
Following a Monte Morris floater to put the Nuggets up 123-121 with 33 seconds remaining, Kerr called a lob for Andrew Wiggins off the inbound from the consequent timeout.
Austin Rivers' steal of Otto Porter Jr's inbound pass effectively sealed the win for Denver, but it came in the face of Curry and Thompson in good shooting rhythm.
"Yeah, I would like that play back," Kerr said. "There's 33 seconds so we're thinking a two-for-one. If we get a two-for-one, then we can tie the game and have a chance to win it at the end.
"So it's a good two-for-one situation, but the lob wasn't there, and if I could do it do it again I'd probably draw up something different. But they made a great defensive play, give them credit."
Ferrell warmed up with the Warriors dressed in a Jackie Moon outfit from the film Semi-Pro that he starred in for the 2008 movie.
Five-time NBA All-Star Thompson never grew tired of watching the film during a long rehabilitation from major knee and Achilles surgeries.
Ferrell might be cast for another appearance at Chase Center after Golden State snapped a five-game losing streak with a commanding 112-97 victory.
Thompson, who scored 20 points and claimed five rebounds, dressed as Moon for Halloween three years ago and was pinching himself after Ferrell helped the Warriors stop the rot.
He said: "When I had some dark days, I would put that movie on, and it would make me smile. I'm very thankful for that film.''
He added: "That was so cool. Dreams do come true."
Warriors head coach Steve Kerr felt Ferrell's presence would lighten the mood after such a poor run.
"He actually emailed me a while back and I didn't believe it was him," Kerr said. "So, we exchanged a couple of emails and concocted a plan.
"You know he is a huge Klay Thompson fan, and he knows how much Klay loves dressing up as Jackie Moon, so it felt like a natural fit and it felt like the time to do it, too – make everyone laugh in a tough stretch in the season and he was great.
"He came into the locker room and made the guys laugh. Everybody loved seeing him and hearing from him. He's hilarious. It was just something different."
Warriors star Stephen Curry, who passed Chris Mullin for the most steals in the franchise's history, said of Ferrell's presence: "It was fun, and I'm glad we took advantage of it.
"I think we fed off the energy. I was actually surprised, his form, he actually had some good rotation on the ball, and endless energy. I don't know how."
