Novak Djokovic crushed Lukasz Kubot 6-2, 6-4 as the top seed at the Swiss Indoors showed on Thursday that his untouchable form is rapidly returning after six weeks out with injury.
Djokovic, who had to struggle in his opening match over three sets, was absolutely untroubled by the Polish qualifier ranked 64th in the world, going through to the quarter-finals in just 54 minutes.
"Today was a really comfortable match," said the world number one. "I felt good on court. I'm happy to be playing better.
"This was the goal, I expected that I would struggle with rhythm after not playing for six weeks. But I have no complaints with my game.
"It was a good performance and I'll try to do better tomorrow."
Champion in 2009 and a losing finalist against Roger Federer in 2010, Djokovic will now face in-form Florian Mayer, who followed up a third-round upset of Rafael Nadal in Shanghai with a 6-3, 6-1 defeat of Ivan Ljubicic.
"I'm surprised by this win, but I have so much confidence from beating Nadal. I know on my best game I can defeat anyone," said the 22nd-ranked Mayer.
Djokovic lifted his impressive 2011 record to 66 wins and three defeats as he won again after overcoming a back injury that he called the worst of his career.
"I'm not 100 percent and to be honest I don't expect to get there this week, I would be surprised if I did. I only started serving a few days before my first match and I could tell I was lacking rhythm on second serve. But it was getting better today.
"I need to stay positive and increase the rhythm and intensity of each match."
Japan's Kei Nishikori continued his Shanghai momentum after a run to the semifinals in China.
The 21-year-old, who stands as Asia's best-ranked player with a 32nd ranking, easily overcame Italian Andreas Seppi 6-3, 7-6 (7/4).
The week ended early for American James Blake, with the 31-year-old exiting at the hands of Mikhail Kukushkin 6-3, 6-4.