Stefanos Tsitsipas is still a chance for an ATP Finals spot, winning his opening match at the Paris Masters against Roberto Carballes Baena 4-6, 6-3, 6-3.

Tsitsipas shook off a difficult start to overcome the Spaniard in one-hour, 59 minutes, hitting 36 winners to Carballes Baena’s 15 to book a second-round berth.

“I didn’t start so well. I had an upset stomach and wasn’t feeling so great on the court,” the Greek said after his match.

“I couldn’t even pump myself up at the beginning of the match, because when something is bothering you that much, it takes your entire concentration and focus.

“That was perhaps the second battle I was facing today, along with my opponent.”

The 26-year-old has reached the semi-finals in Paris in each of the past two years and is chasing a sixth straight ATP Finals appearance.

Ranked 12th in the ATP Live Race To Turin, he’ll need a deep run to earn a spot in the season finale.

Last week he reached the quarter-final at the Swiss Indoors but came up short against Arthur Fils.

“It’s going to take a lot for me to qualify, so if I manage to up my tennis during this entire week, let’s see,” the 11-time title winner said.

“If I’m able to deliver something good here, I guess that also earns me a spot in Turin. Regardless of that. I’m just trying to improve and feel my game the best I can.”

Tsitsipas immediately broke his opponent’s serve for 3-1 and had no trouble holding firm behind his delivery from there to level the match. He then bookended the deciding set with further breaks of Carballes Baena’s serve.

Having started the match slowly, he eventually improved to win 80 per cent of points behind his first delivery, and the key was his improved physical state.

“It took a long time for me to feel better,” he said.

“It was very strange. It doesn’t happen very often. I just had to feel better, because I knew I was playing good tennis. I didn’t have a great start, but there were so many things on my mind at that moment, I wasn’t able to play clearly and with a good picture.

“Eventually I found the tennis that I wanted. It took a while to get to that point, but I knew that if I got to the point of feeling my game and aligning with my shots, it perhaps would have been enough to win that match.

“He wasn’t giving me much. I knew that he was going to fight but I knew I had some weapons that could hurt him a lot and I used those towards the end.”

The World No.11 will next face Alejandro Tabilo in the Round of 32, scheduled for tomorrow 2.50am AEDT.