Thiem has struggled for form since winning his first grand slam title at the US Open last September but looked to be finding a way past Andujar when he opened up a two-set lead.

However Andujar, who beat Roger Federer in Geneva last week, fought back to win 4-6 5-7 6-3 6-4 6-4 and record his first victory over a top-five player at the age of 35.

Thiem took a six-week break in March and April to step back from the demands of the tour and bubble life and must now reflect on a first opening-round loss at Roland Garros.

The 27-year-old, who was seeded fourth, has reached at least the quarter-finals on his previous five visits, losing to Rafael Nadal in the final in 2018 and 2019.

"I was not struggling at all with my motivation but the game was just not there today," Thiem said.

"All the shots are missing power. They are not accurate enough.

"I'm moving not well enough, so everything in my game, there are some percentages missing... It's just not good enough at the moment. And it's a very tough situation."

Meanwhile, sixth-seeded Alexander Zverev rallied from two sets down to beat qualifier Oscar Otte 3-6 3-6 6-2 6-2 6-0 in his opening round clash.

The 24-year-old Zverev seemed to be heading for an early exit like Thiem but he found a different gear to turn around the contest.

For the rest of the match, it was one-way traffic against the 152nd-ranked Otte in the first meeting between the two Germans.

"I couldn't find my rhythm. In the third set I decided to hit the ball a little harder, hit the forehand a little heavier as well and managed to turn it around," Zverev said in his on-court interview.

With Novak Djokovic, Nadal and Roger Federer all being placed in the top half, it is a golden chance for players in the bottom half to reach the final, and Zverev admitted Thiem's loss affected him.

Stefanos Tsitsipas is the favourite, along with Daniil Medvedev, to make it through from the bottom half and he saved a set point before cruising past France's Jeremy Chardy 7-6 (8-6) 6-3 6-1 in a match played without fans because of Paris' 9pm curfew due to coronavirus restrictions.

Orher first-round winners included Roberto Bautista Agut, Pablo Carreno Busta, Karen Khachanov, Kei Nishikori and Fabio Fognini but 16th-seeded Grigor Dimitrov is out, forced to retire with a back problem after having match points against Marcos Giron.

PA/Reuters

Australian Associated Press