Top seed and world No. 1 Roger Federer faced a tough test in his first-ever appearance at the AIG Japan Open on Wednesday before dispatching qualifier Viktor Troicki 7-6 (7-2), 7-6 (7-3) at a packed Ariake Colosseum.

News photo Andy Murray returns the ball during his 3-6, 6-7 (1-7) loss to Jiri Novak on Wednesday in the Japan Open. AP PHOTO

Federer, who received a first-round bye, would have been forgiven for expecting an easier start to the Tokyo tournament, but came up against a plucky 20-year-old making his debut in an ATP event -- and the Serbian showed little sign of stage-fright.

"It was a really tough match," Federer said later. "I didn't know his game. I've never seen him play and it always takes time to figure a player out."

Troicki, ranked No. 272 in the world, troubled Federer with a booming serve -- one touched 200 kph -- and a forehand that kept Federer pinned back for much of the game, with the Swiss star only breaking away on the two tie-breaks.

Said Federer: "I couldn't get a read on his serve. He mixed it up well. This was my first match of the tournament so I wanted to play it safe and get (into) a rhythm."

Federer came into the tournament on the back of another phenomenal year. The Swiss star has won three of the four grand slam tournaments in 2006, with just a defeat to Rafael Nadal in the final of the French Open denying him a clean sweep.

The 25-year-old's only losses since the start of June have come at Roland Garros and in the second round in Cincinnati to Andy Murray.

Federer will be up against last year's champion, Wesley Moodie, in the third round after the South African No. 13 seed downed Austria's Stefan Koubek 6-3, 6-4.

In the women's singles, Japan's No. 2 seed, Ai Sugiyama, eased past Finland's Emma Laine 6-4, 6-3 and will play Vania King in the second round after the American beat France's Severine Bremond.

An upbeat Sugiyama, ranked No. 27 in the world, said she is enjoying her tennis now more than at any other point in her career -- even than when she hit a career-high eighth in the world in 2004.

"I had a great year in 2003 and 2004 but my motivation went down a bit after that and it's not easy to have high motivation all the time," Sugiyama said. "But now I am enjoying the game the most in my career and I am looking forward to working hard and playing hard.

"It goes up and down but I want to get back into the top 20, and then the top 10."

In an earlier women's game on center court, Japan's Junri Namigata beat Colombia's Catalina Castano 6-2, 1-6, 6-4 to advance to a second-round tie against Argentina's Paola Suarez, who beat the Czech Republic's Lucie Safarova 6-4, 6-4.

Meanwhile, No. 4 seed Murray won't get the chance to repeat August's victory over Federer as he crashed out of the tournament in the second round against Czech veteran Jiri Novak.

The Scottish firebrand received a bye in the first round and never got going against the 2004 champion, only briefly threatening in the second set before going down 6-3, 7-6 (7-1).

Murray's disappointing exit comes after a first-round defeat to Tim Henman at the Bangkok Open, but the British No. 1 refused to blame his poor form on a hectic schedule.

"Every single young player goes through stages where they play well and then don't play well," the 19-year-old Murray said. "It's not as though I've played against two bad players (in Henman and Novak) . . . it's not due to the schedule I've lost.

"I did well to fight my way back into the match today, but couldn't quite turn it around."

Murray's interest now rests in the men's doubles and he will hope his partnership with brother Jamie Murray can continue to blossom after their recent run to the Bangkok Open final.

In another second-round tie, No. 2 seed Tommy Robredo powered past Lu Yen-Hsun of Taiwan 6-4, 6-1.