(CNN) -- Marin Cilic made a winning return to the ATP circuit Monday after serving a reduced doping ban.
The 25-year-old Croatian completed a tight three set victory over Dutchman Igor Sijsling at the Paris Masters, prevailing 5-7 6-1 6-4 at Bercy Stadium.
Cilic has slipped to World No.47 after testing positive for the stimulant nikethamide at the Munich Open in May.
He was banned for nine months by an independent tribunal in September, but his appeal to the Court of Arbitration for Sport saw his suspension cut to four months last Friday.
The decision allowed Cilic to enter the final regular season tournament on the main tour in the French capital and he took full advantage.
Despite losing the first set, Cilic earned a second round match against in form World No.5 Juan Martin Del Potro of Argentina.
He later admitted that he was pleased to put the experience behind him and return to action.
"I would definitely say it was the worst time of my life as a player," he told AFP.
"I have been on the tour for six, seven years, and have been always really careful and really honest and fair as much as I could with all the other players.
"And then to be in that kind of situation where when I found out about the positive test it was an extremely difficult situation where people were even calling me a doping player and a cheat.
"I knew I didn't cheat," added Cilic.
World No.1 Rafael Nadal, who is playing in Paris for the first time in four years, told gathered reporters that he was delighted to see Cilic return to action.
"One thing I can say is I'm happy to see Marin back on tour. He's a good guy and a great player," he told AFP.
"I don't know what happened but if he's back, it's because it's fair that he's back. That's all. I'm happy for that."
Nadal will open his campaign later in week but the early headlines will surround players attempting to book their passages to the ATP World Tour Finals in London.
Roger Federer, Swiss colleague Stanislas Wawrinka and French duo Richard Gasquet and Jo-Wilfried Tsonga are battling for the final three places in the elite eight-man field, with four others having mathematical chances of qualifying.
Wawrinka learned his second round opponent in Paris as Spaniard Feliciano Lopez won a tight encounter against Australian qualifier Bernard Tomic 6-4 6-7 7-6 Monday.
Federer, who needs one win to clinch a 12th consecutive appearance in the finals, will face the winner of the first round match between Kevin Anderson and Mikhail Zouzhny, while Gasquet and Tsonga could meet in the third round of their home event.
World No.2 Novak Djokovic claimed the ATP finale last season, beating Federer in the final, while Nadal has never claimed the title.
The Spaniard hopes to use a good performance in Paris as a springboard to success in London.
"The last tournament of the year is important," he told the official ATP Tour website.
"In 2010 I played well (lost in the final to Federer); the rest I played really bad. I want to try to change that.
"I was always motivated for this last part of the season, but I was not able to apply it well. I hope this year I can change that situation. I hope to play well here and then we'll see."