Brisbane - Reigning US Open champion Stan Wawrinka was in impressive form as he saw off Serbia's Viktor Troicki in straight sets to move into the quarter-finals of the Brisbane International on Wednesday.
In a high quality match, the Swiss world number four took just under 90 minutes to defeat Troicki 7-6 (7/5), 6-4.
Wawrinka, 31, has traditionally played in Chennai at this time of year but said he wanted to change his Australian Open preparations.
"I'm quite happy with my level to start the year," he said.
"It's always tough to play against Troicki, and I'm very happy for the first match.
"I'm just enjoying a new tournament that I never played, that I'm playing for the first time.
"New facility, new court, new fans, new city, and that's what make the difference. Especially at 31 years old, when you've been on the tour for so long, to play some new tournaments, it makes you a little bit fresher mentally, also."
Wawrinka will now take on unseeded Briton Kyle Edmund in the quarter-finals of the season-opening event.
Edmund progressed when French opponent Lucas Pouille was forced to retire hurt during their match with blisters on his right foot.
Edmund won the first set 6-3 but after Pouille took the opening game of the second set he called for attention from the trainer.
However, after losing the next two games the sixth seeded Frenchman decided he could no longer continue and handed Edmund the match.
Earlier, a rusty Kei Nishikori survived a scare from qualifier Jared Donaldson.
The third seeded Japanese lost the first set to the American, ranked 105, but recovered to take the match 4-6, 6-4, 6-3 in two hours, 25 minutes.
Nishikori, who had a first round bye, looked out of sorts as he let early leads slip in the first two sets.
But once he got in front in the third he was able to keep control and book a last-eight place against Australian wildcard Jordan Thompson, who stunned eighth seed David Ferrer of Spain.
"Actually, I had a great start today until four-love, and then I had one bad game," Nishikori said.
"After that he started playing much better. He started playing more aggressive, and his forehand was on fire today.
"It was really close. Even the second set it was really close. He had many chances to win the set and win the match."
Thompson reached an ATP quarter-final for the first time when he beat Ferrer 4-6, 7-5, 7-5 to the delight of the big crowd at Pat Rafter Arena.
He said he wasn't daunted at the prospect of playing Nishikori.
"I think you've got to give yourself a chance no matter who you play," he said.
"Otherwise there's no point in taking the court."
Results from the fourth day of the ATP/WTA Brisbane International tennis tournament on Wednesday (x denotes seed):
Kei Nishikori (JPN x3) bt Jared Donaldson (USA) 4-6, 6-4, 6-3
Kyle Edmund (GBR) bt Lucas Pouille (FRA x6) 6-3, 3-1 (ret)
Jordan Thompson (AUS) bt David Ferrer (ESP x8) 4-6, 7-5, 7-5
Stan Wawrinka (SUI X2) bt Viktor Troicki (SRB) 7-6 (7/5), 6-4
Dominika Cibulkova (SVK x2) bt Zhang Shuai (CHN) 2-6, 6-4, 6-4
Svetlana Kuznetsova (RUS x5) bt Destanee Aiava (AUS) 6-4, 6-3
Roberta Vinci (ITA x8) bt Misaki Doi (JPN) 6-4, 6-2
Angelique Kerber (GER X1) bt Ashleigh Barty (AUS) 6-3, 2-6, 6-3