Croatia's Marin Cilic marked his return from a doping ban with a first round victory at the Paris Masters on Monday and expressed his delight at being back on court.
His hard fought three set victory over Dutchman Igor Sijsling was the perfect tonic following a difficult time for the former Grand Slam semi-finalist.
Cilic, 25, currently ranked 47th in the world, tested positive for the stimulant nikethamide at the Munich Open in May and was banned for nine months by an independent tribunal in September.
However the Court of Arbitration for Sport (CAS) reduced the ban to four months last Friday meaning the sanction expired one day later and allowed him to take his place in the tournament.
After dropping a tense opening set, Cilic bounced back to set up a matchup against world number five Juan Martin Del Potro of Argentina with a 5-7, 6-1, 6-4 victory.
"I felt like a kid playing tennis for the first time," said an exuberant Cilic, who reached the 2010 Australian Open last four and quarter-finals of the US Open in 2009 and 2012.
"And I would say the feeling was amazing just to be back on the court, to be competing, and I enjoyed every moment.
The Croatian admitted it had been a nightmare.
"Yeah, I would definitely say it was the worst time of my life to experience this as a player.
"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, and then also the media started to write and it was extremely difficult situations where people were even calling me a doping player and a cheater.
"I knew I didn't cheat, and the most important, I haven't taken anybody's prize money and I haven't beat anybody in that tournament
Cilic said that he and his fellow professionals had to be extremely careful in what they consumed.
"I'm of course definitely against doping, against the players who are cheating.
"I mean, even sometimes now these days I'm even looking in Gatorade. Always drinking closed bottle, because you have to be careful with all the things.
"It's not a fun thing to go to the hearings, and I wouldn't recommend that to anyone because it's very, very stressful and definitely it leaves a big scar on anyone."
Also on Monday, in a programme which featured only unseeded players, Spaniard Feliciano Lopez edged a fiercely contested match against Australian qualifier Bernard Tomic 6-4, 6-7 (4/7), 7-6 (7/1).
Lopez will now meet Stanislas Wawrinka with the Swiss seventh seed looking to wrap up his first ever appearance at the London Masters with a good run this week.
Wawrinka is battling with compatriot Roger Federer, and French duo Richard Gasquet and Jo-Wilfrid Tsonga for the final tickets to the eight-man tournament in the English capital.
Elsewhere, on a disappointing day for French players Jeremy Chardy, Adrian Mannarino and Julien Benneteau were all eliminated.
Chardy who began the season with a run to the Australian Open quarter-finals was well beaten 6-3, 6-4 by Czech Lukas Rosol, while Mannarino suffered a tough three set defeat against Colombian Santiago Giraldo 6-3, 2-6, 6-4.
Doubles' specialist Benneteau who was a 2011 finalist in Paris along with Nicolas Mahut ran into an in-form Kei Nishikori and won only six games during a 6-4, 6-2 defeat against the Japanese world number 18.
Nishikori will now play French number one Jo-Wilfried Tsonga for a place in the last-16 on Tuesday.
Elsewhere, Dutchman Robin Haase clinched the first set 10-8 in a tie-break before closing out his match 7-6, 6-3 over Denis Istomin of Uzbekistan and German Philipp Kohlschreiber outlasted Andreas Seppi of Italy 6-3, 3-6, 6-4.