But the new kid on the block, Spanish teenager Carlos Alcaraz, steamrolled past Argentine lucky loser Juan Ignacio Londero 6-4 6-2 6-0.

Thiem capitulated 6-3 6-2 6-4 in just over two hours. The Austrian, who has failed to win a match at any of the tournaments he has played since his wrist injury comeback in March, made 42 unforced errors as his once-dominant claycourt game deserted him on Sunday.

"It was not a good match at all but it is what it is," Thiem, ranked third in the world in 2021 compared to his current 194th, said.

"I knew it would take time and the level is extremely high. It is going to take a few more months until I say now I am ready to beat those guys again."

The 28-year-old struggled with his forehand throughout the match and said it was now time to compete in lower-tier tournaments to get match wins under his belt.

"The problem is in practice it is really decent but a match situation is something different, Grand Slam especially. I am definitely thinking to go back to Challenger level for one or two tournaments," he said.

"I am more tight, more nervous and the whole body gets more tight. This is toxic to my forehand because I am still missing the fine feeling there," he said.

Dellien, comfortable on the surface after battling through the qualifiers to reach the main draw in all five claycourt tournaments preceding Paris, did not have to wait long for his chance.

He earned his first break point in Thiem's opening service game and broke him on his second to race through the first set.

Two quick breaks in the second wrapped it up for Dellien, with Thiem, who injured his wrist in Mallorca in 2021 and required surgery, struggling with for consistency throughout.

Alcaraz, who won the Barcelona Open and the Madrid Masters in the run-up to Roland Garros, needed just one set to adjust to the immense Court Philippe Chatrier to set up a meeting with fellow Spaniard Albert Ramos-Vinolas.

The 19-year-old sixth seed, who reached the third round as a qualifier last year in Paris, has won four titles this year and arrived at the French Open established as one of the title favourites.

He said: "This tournament is very special, I've been watching it since I was a kid,"

Elsewhere Canadian ninth seed Felix Auger-Aliassime fought back from two sets down to beat Peru's Juan Pablo Varillas 2-6 2-6 6-1 6-3 6-3.

German third seed Alexander Zverev had an easier passage, winning 6-2 6-4 6-4 against Austrian qualifier Sebastian Ofner.

He joked: "Usually I start a Grand Slam tournament with a five-set match and a few hours on court, but (coach) Sergi (Bruguera) told me today not to do that so I listened to him for once."

Big-serving American John Isner converted only one break point but won three tiebreaks against Quentin Halys to advance with a 7-6 (7-3) 4-6 7-6 (7-1) 7-6 (7-6) victory.

With Reuters

Australian Associated Press