Novak Djokovic said both he and Roger Federer will need to produce their 'A' game when they face each other in the semi-finals of the Shanghai Masters.
The Serbian world number one eased to a 6-4 6-2 win over David Ferrer in his last-eight match, while 17-time Grand Slam winner Federer overcame Frenchman Julien Benneteau 7-6 (7-4) 6-0.
"It's really a big challenge for both of us," said the two-time champion.
"We need to bring our 'A' game in order to win."
The pair will be playing each other for the 36th time, with 33-year-old Federer edging the head-to-head 18-17.
"We'll see how much he can actually do, how much he can neutralise me, and how much I can do with him," said the Swiss, who will replace Rafael Nadal as world number two when the rankings are updated next week.
"But he's playing a great season again. I'll give it the best shot I have. I have a good game at the moment."
Both go into the match following two imperious displays. Defending champion Djokovic hit 26 winners against Spaniard Ferrer's 11, to stretch his winning streak in China to 29 matches.
Federer served 11 aces, won 91% of his first serve points and smashed 34 winners - double the tally Benneteau could manage.
The other semi-final will feature Gilles Simon and Feliciano Lopez.
Spaniard Lopez, 33, who knocked out an unfit Nadal in the second round, defeated Mikhail Youzhny 5-7 6-4 6-4 in his quarter-final match.
Simon, 29, beat a second top 10 player in a week, with a 7-6 (7-4) 4-6 6-0 win over sixth-seed Tomas Berdych.
The Frenchman knocked out fourth-seed Stan Wawrinka in the second round.