The Norwegian grandmaster suffered a surprising defeat against Vladislav Artemiev at the Chessable Masters on Monday, the second-leg of the new lucrative Champions Chess Tour.
Carlsen set the tone with a rare blunder in the opening game and never really found the form that has made him one of the most formidable players in history.
He went on to lose two games with white, something which rarely happens, and found himself 2-1 down in the best-of-five match, needing a win in the final game.
The thought of beating Carlsen seemed to throw Artemiev off his game and the Russian made a string of blunders to hand the reigning world champion a route back via an Armageddon tiebreaker.
The 32-year-old, though, couldn’t capitalize on the opportunity and made another game-losing blunder to hand Artemiev the victory.
“It was pretty bad. He generally outplayed me,” Carlsen said after the loss. “The last game was terrible.”
“This was a really, really awful day of chess. I did everything to lose – and then some,” he continued.
“Obviously, it takes a strong opponent to exploit that, but that was really poor.”
Carlsen has a chance to redeem himself on Tuesday when he plays Le Quang Liem in the losers bracket of the tournament.
If he loses again, he’ll be eliminated from the tournament.
“I will do my best tomorrow, but this is unacceptable,” he added.
Elsewhere, US grandmaster Hikaru Nakamura overcame a tricky match to beat Vladimir Fedoseev in a tiebreaker.
He will join Fabiano Caruana, Wesley So and Artemiev in the winners bracket.
What is the Champions Chess Tour?
The Champions Chess Tour is the new online home for the world’s best players, as they battle it out for a share of more than $2 million.
Played on website Chess.com, the annual circuit consists of six tournaments, which started with the Airthings Masters in February – an event won by Carlsen.
Every event has a $235,000 prize fund and the winners of each will qualify for an eight-player, live finale in December which has a purse of $500,000.
A further $100,000 will be shared among the top 10 finishers in the overall standings.