World No 1 Novak Djokovic endured a tough return to the ATP singles circuit but battled through to beat Marton Fucsovics of Hungary 6-2, 4-6, 6-3 in the second round of the Paris Masters on Tuesday.

The 34-year-old 20-time Grand Slam champion had said on Sunday his greatest fear was lack of match practice having not played since Daniil Medvedev dashed his dreams of a Grand Slam sweep in the US Open final in September.

The Serbian's fears were borne out as Fucsovics put up a sterner test than the 'rabbit caught in the headlights' one he had produced when they met in the Wimbledon quarterfinals earlier this year.

"It is my return to competition after almost two months of not playing in an official tournament," said Djokovic.

"Thus it was difficult to get into my rhythm but I am happy it is a decent win."

Djokovic – who rare for him is also playing the doubles in Paris – said he expected a tough match despite having beaten his opponent the three previous times they had met.

"It was a super battle," he said.

"Now I must play more to rediscover my level of intensity.

"The more matches I play the better I will play.

"I know this well as I have been in this situation before. Hopefully that experience will be useful."

Djokovic barely had to engage second gear when cruising to the first set in 38 minutes with the loss of just two games.

But Fucsovics broke early to go 3-1 up in the second, energising the evening crowd at Bercy.

Djokovic served to save the set to love at 5-3, but the Australian, French and Wimbledon champion was unable to prevent Fucsovics serving out to take the match to a decisive set.

Djokovic, though, pulled it together in the third set and broke his 29-year-old opponent to go 4-2 up.

Djokovic had a match point on Fucsovic's next service game as he turned the screw but the Hungarian saved it and stayed in the contest by winning the game to trail 3-5.

Djokovic, though, made no mistake when he served for the match to see off his 40th-ranked opponent and progess to the third round.

He will play the winner of the all-French clash between Adrian Mannarino and mercurial Gael Monfils.

Earlier another seed had had a tough time of it as well.

Felix Auger-Aliassime set up a second round clash with Domink Koepfer, conqueror of Andy Murray, after coming from a set down to beat Italian qualifier Gianluca Mager 4-6, 6-4, 6-1.

The 21-year-old Canadian ninth seed needed five match points to do so against a dogged opponent, who played way above his world ranking of 66.

Auger-Aliassime will need to be on his mettle when he faces Koepfer who saved seven match points against world No 1 Murray on Monday before sealing victory with his first.

"The end of the first set was disappointing but I reacted well," said Auger-Aliassime.

"I bounced back in the second set.

"After returning so well, I created occasions and I won the second set and then I finished very well.

"So the match was indeed with an upward phase which was positive for me."

Auger-Aliassime has been very much also on an upward phase including reaching the US Open semifinals although aided by his quarterfinal opponent Carlos Alcaraz retiring from the match with a thigh injury.

The 18-year-old Spaniard, though, has recovered and showed real toughness in overcoming Frenchman Pierre-Hugues Herbert 6-7 (4/7), 7-6 (7/2), 7-5 in a thrilling see-saw encounter which lasted seven minutes shy of three hours.

Herbert, fired up by a partisan crowd, had saved two match points but then limply handed victory to Alcaraz with his 10th double fault of the match.

Alcaraz will face the in-form Italian eighth seed Jannik Sinner in the second round in what promises to be a cracking encounter of two of the up and coming young talents. (AFP)