Novak Djokovic on Tuesday added his voice to calls for a re-think of the late-season ATP calendar, admitting that he is having to work hard to hold up physically through this week's Paris Masters to the year-ender in London.

The Serb, who will finish the season as world number one for the second year running, said he is trying to conserve his strength for the final competitive sprint -- even in a season shortened by a fortnight.

"It is a big challenge," he told a news conference in the French capital.

"Obviously I'm sure all the participants in London will agree that this (ending the pre-London preparation week) is definitely not something that goes in the favour of us preparing for the most important event in the end of the year."

The last two spots in the World Tour Finals will be decided during play this week.

Djokovic himself has not played since beating Britain's Andy Murray for the title in Shanghai this month, then resting for two weeks.

While Djokovic and Murray are competing in Paris, current world number one Roger Federer is not, with the Swiss taking a break before the start of the eight-man World Tour Finals on Monday.

Djokovic, whose own health (possible stomach virus) and that of his father, who is reportedly ill in a Belgrade hospital, have been the subject of speculation in recent days, said nothing on either matter.

Instead, he indicated that he feels wiped out after a long season during which he and his team have tried to conserve strength for the run-in.

"This is the schedule. It is the way it is. We have to adjust, we have to accept it," he said. "Unfortunately, there is no other options at this moment.

"But we will discuss this matter after we finish this season. Maybe we can try to find some other way.

"This season is shorter by two weeks. Now we have a two weeks longer off-season. Maybe that was the sacrifice we had to make.

"There are still some options on the table about this (pre-London) week. Maybe we can move it around so we can make it more adjustable for the top players."

Djokovic added: "Physically I feel good now, but I'm not the freshest guy on the Tour because I have had a long year. But I want to try to hold on these two weeks and perform my best, and then go to holidays."

On court, France's men continued to impress in front of the home public.

French sixth seed Jo-Wilfried Tsonga stayed in the race for the penultimate position in the year-end finals field as he beat compatriot Julien Benneteau in a 6-2, 4-6, 7-6 (7/2) second round struggle lasting for more than two hours.

Tsonga can clinch his place in the London field by winning just one more game here to reach the quarter-finals, according to ATP calculations.

Wild card Paul-Henri Mathieu, who missed 2011 with a knee injury, came through his first round clash in dramatic style over Spanish qualifier Robert Bautista-Agut 6-4, 7-5.

The number 64, who reached the Basel semi-finals last weekend, was broken while serving for the match in a game which lasted an incredible 27 minutes and featured 15 deuces and 12 break points.

Bautista-Agut finally won it for five-all only to lose serve again as Mathieu squeezed through to set up a match with third-seed Murray.

Compatriot Jeremy Chardy will play Canadian Milos Raonic as he defeated Guillermo Garcia-Lopez of Spain 6-0, 6-3.