Jannik Sinner wasted two match points as he was knocked out of the French Open 6-7(0), 7-6(7), 1-6, 7-6(4), 7-5 in a second round thriller against German Daniel Altmaier on Thursday.

The red-haired Italian, who is often cheered on by six fans dressed as carrots - the Carota boys - and was spotted eating carrots as an on-court snack in Vienna, was not his dominant self as he bowed out after five hours 26 minutes.

Eighth-seeded Sinner, whose best performance at Roland Garros came in 2020 when he lost in the quarter-finals against Rafael Nadal, looked set for a no-nonsense win after cruising through the third set but Altmaier had other ideas.

While Sinner's hard-hitting approach works on hard courts, he struggles on the slowest surface, which proves more challenging, and he was eventually worn down by the world number 79, who won on his fifth match point on Court Suzanne Lenglen.

"Usually I'm smiling inside and that was not the case today, my attitude was not right, I did things I don't usually do," Sinner, who at one point smashed his racket onto the court - very rare behaviour from him - told a press conference.

"This year I have this goal to qualify for (the ATP Finals in) Turin and maybe I put too much pressure on myself, having this objective. So maybe I need to change my mindset."

After an exchange of breaks, the first set was decided in a tiebreak in which Sinner won all the points.

The second set was a carbon copy of the first until the tiebreak, which Altmaier dominated, winning most of the long rallies.

It looked like the Italian would hop into the next round as he blazed through the third set, but he paid for his efforts in the fourth, finding himself trailing 3-0. He rallied back, however, and broke for 5-4.

Sinner then wasted two match points - one when Altmaier's passing shot clipped the net and took him by surprise - as the German stole his serve again to send the match into a decider.

Altmaier, who reached the quarter-finals in Madrid this year and the last 16 at Roland Garros in 2020, served twice for the match, eventually shaking off his nerves to end it with an ace.

He went back to his chair as tears rolled down his cheeks before saying: "I love the game of tennis. In the past months, me, my team, we put so much effort all together.

"We play here but behind us we have strong teams, that's why this victory is a team effort."