Defending champion Novak Djokovic reached the French Open second round for the 20th time on Tuesday but insisted he "won't get too excited" after enduring a worrying decline in form and achievements this season.

Djokovic, chasing a fourth title at Roland Garros and record 25th Grand Slam triumph, came through against 142nd-ranked French opponent Pierre-Hugues Herbert 6-4, 7-6 (7/3), 6-4.

However, without a title or even a place in a final this season for the first time since 2018, Djokovic wasn't getting too far ahead of himself.

"In Monte-Carlo (beaten in the semi-finals), Rome (lost in the 3rd round) and Geneva (beaten in the semi-finals), I started the tournament really well. My first matches were great," he said.

"But the second or third, it was something else... So I don't want to get too excited."

The 37-year-old Djokovic, who saw career-long rival and 14-time French Open champion Rafael Nadal exit the tournament on Monday, arrived in Paris under a cloud.

His best runs were to the semi-finals of the Australian Open, where he lost his title to Jannik Sinner, Monte Carlo and Geneva.

Adding injury to insult he was then accidentally hit on the head by a metal water bottle in Rome and suffered stomach problems at the Switzerland event last week.

"It was a good performance tonight from me," added Djokovic after his 93rd career win at Roland Garros.

"It was solid. I could have done better on the return games, but congratulations to him for serving very well.

"I felt better compared to the previous weeks. I'm moving in the right direction. But it's only the beginning. It's only one match. We have to see how I will progress in the tournament, how my feelings will evolve."

Djokovic, who has advanced to the French Open quarter-finals or better every year since 2010, will face Spain's Roberto Carballes Baena for a place in the last 32.

"I'm happy with my state of mind on the court, it's something I was looking for," added Djokovic.

"And where are you going to feel that if it's not in the Grand Slams? I've been saying it over the last few years, the Grand Slam tournaments are the ones that make me get up every morning and go train. I hope to go far once again."