(CNN) -- He came out on court wearing a Halloween mask, but Novak Djokovic had to overcome a fright of his own before winning his comeback match in Switzerland on Tuesday.





The world No. 1, playing his first ATP Tour tournament since winning the U.S. Open six weeks ago, survived a second-set scare against Xavier Malisse before beating the Belgian 6-2 4-6 7-5 at the Swiss Indoors event.





Djokovic suffered a recurring back injury in Serbia's Davis Cup defeat by Argentina just days after beating Rafael Nadal in an epic final in New York.





He missed tournaments in Asia, including the Shanghai Masters, but has returned to action in Basel where he was champion in 2009 and runner-up to Roger Federer last year.





"I'm only just back from the biggest injury of my career," Djokovic said after extending his record this year to 65-3. "It was a big ask for me to have played really well.





"I could do nothing for four and a half weeks, I've only been hitting for a week and a half. That's not enough to play at my best. I've lost rhythm.





"I had too many errors and too many double-faults. But I'm happy just to be playing tennis again. I hope to build on this performance."





As top seed, he is in the opposite half of the draw from Federer and new world No. 3 Andy Murray, who could meet in the semis.





The 24-year-old will next play either Poland's world No. 59 Lukasz Kubot or 91st-ranked German Tobias Kamke, who both came through the qualifying draw.





Fifth seed Mardy Fish's hopes of qualifying for the season-ending ATP World Tour Finals suffered a blow when he was forced to retire with a hamstring injury against fellow American James Blake after winning the opening game.





Fish holds the last of the eight places on offer for the London showpiece but could be overhauled if he has to miss the penultimate tournament in Paris starting next week.





Blake will next play Kazakhstan's Mikhail Kukushkin, a lucky loser from qualifying who upset American wildcard Donald Young in his opening match.





Stanislas Wawrinka, a semifinalist in 2006 and the Swiss No. 2 behind Federer, beat Croatia's Ivan Dodig 6-4 6-4 to set up a match with either Murray or Dutchman Robin Haase, who meet on Wednesday.





Federer's next match is against Jarkko Nieminen, after the Finn beat Brazil's Thomaz Belluci 6-7(5-7) 6-4 6-3.





Tomas Berdych had the sixth finals place ahead of his clash with Japan's Kei Nishikori, but the Czech failed to earn any ranking points after losing 3-6 6-3 6-2.





Seventh-ranked Frenchman Jo-Wilfried Tsonga closed to within five points of Berdych by winning his opening match at the Valencia Open on Tuesday.





Tsonga had to battle before beating 19-year-old Spanish wildcard Javier Marti 4-6 7-5 6-2 to secure his 12th win in 14 matches and set up a second-round clash with American Sam Querrey -- who defeated Latvia's Ernests Gulbis 6-4 6-4.





Top seed David Ferrer is one of the five players already qualified for London, and he overcame fellow Spaniard Fernando Verdasco 6-3 6-2 in his opening match to set up a meeting with Canadian qualifier Vasek Pospisil.





French third seed Gael Monfils went through with a 6-3 6-1 win over Albert Montanes, but Ukrainian seventh seed Oleksandr Dolgopolov Jr. was eliminated by another Spaniard, Marcel Granollers.
whats Serbian beats Belgium's Xavier Malisse in three sets, but complains of being rusty? Who beats Xavier Malisse in three sets? Where Novak Djokovic wins his first match in six weeks? What happened to Mardy Fish? What was the score of the winning match? Where did Jo-Wilfried Tsonga have an opening win in the ATP World Tour?
Novak Djokovic Novak Djokovic Switzerland forced to retire with a hamstring injury 6-2 4-6 7-5 Valencia Open
question: whats Serbian beats Belgium's Xavier Malisse in three sets, but complains of being rusty?, answer: Novak Djokovic | question: Who beats Xavier Malisse in three sets?, answer: Novak Djokovic | question: Where Novak Djokovic wins his first match in six weeks?, answer: Switzerland | question: What happened to Mardy Fish?, answer: forced to retire with a hamstring injury | question: What was the score of the winning match?, answer: 6-2 4-6 7-5 | question: Where did Jo-Wilfried Tsonga have an opening win in the ATP World Tour?, answer: Valencia Open