Rafael Nadal and Djokovic are battling out for the year-end world No 1 ranking in the final two tournaments of the season.
Djokovic has to better his Spanish rival’s results this week to rise to the top of the standings ahead of the ATP Tour Finals.
And the Serbian booked his place in the third round at Paris-Bercy with a 7-5, 6-1 win against Sousa.
However, Djokovic then confirmed he is looking forward to having Wednesday to rest as he is feeling under the weather.
“Very helpful [to have a day off], I’m looking forward to it,” Djokovic said.
“In the important moments, I managed to get the right shots in play.
“I’m not 100 per cent pleased with my game, I missed a lot of shots from the back of the court.
“But at the end of the day, it’s the first match, so it takes a bit of time to adjust.”
Meanwhile, Nadal takes on fellow countryman Fernando Verdasco this afternoon.
But the world No 1 claims his primary objective is not to hold his ranking.
“No, I get injured and I get injured in an important part of the season twice,” Nadal said.
“At the beginning of the season, missing two Masters 1000s, a 500, the Australian Open and then I get injured at the US Open and I miss again Beijing, Shanghai. So too many tournaments lost.
“My main goal is to be back on court, keep being happy playing tennis and then things that can happen or not, let’s see.
“I’m going to fight as strong as I can to win as many matches as possible and of course I would love to be No 1 but I am just here to try my best every day.”
On Djokovic’s recent form, he added: “I’m not surprised at all, he’s so good. At the same time I played only nine events and got injured in two of them and two of them have been Grand Slams.
“He’s having a great second part of the season so he deserves to be where he is.
“Everybody was sure that he would be back at his best and I’m happy to see somebody like him back playing at that high level.”