Roger Federer was in inspired form to beat Andy Roddick 6-4 6-2 and set up a semi-final clash with Rafael Nadal at the Masters Cup in Shanghai.
Federer has won 15 of his 16 matches against Roddick
Nikolay Davydenko's earlier win over Fernando Gonzalez meant Federer reached the last four regardless of whether he beat Roddick, who was already through.
But the world number one still raised his game and out-fought and out-thought Roddick, who was powerless to respond.
The American will face David Ferrer in Saturday's other semi-final.
Federer lost his opening match against Gonzalez but he was back to his masterful best against Roddick, getting the straight-sets win he needed to top the Red Group.
RED GROUP STANDINGS
Federer P3 W2 L1 F5 A2 Pts 2
Roddick P3 W2 L1 F4 A3 Pts 2
D'denko P3 W1 L2 F3 A4 Pts 1
Gonza'z P3 W1 L2 F2 A5 Pts 1
Roddick battled gamely but never looked like putting his opponent in trouble and paid the price for several poor shots at crucial stages of the match.
In contrast Federer produced a terrific all-court display, with his form at the net particularly impressive.
The defending champion has not lost to Roddick since 2003, a run of 11 matches, and he has now won 15 of their 16 meetings.
"I was impressed with my own performance," Federer said. "But let's not overrate today's match," he said. "We had both qualified and we could both play freely."
"If I'm on top of my game, indoors I'm favourite (against Nadal) but it depends on form on the day."
A dejected Roddick added: "It seems like most times we play he's on top of his game, which is a little annoying.
"I have to find out what about my game brings out the best in him and try to adjust."
The pressure could have been on Federer if Gonzalez had beaten Davydenko, who was already out of contention, but the Russian triumphed in an error-strewn match.
Gonzalez produced some memorable individual shots but could not maintain any sort of form and his defeat ensured Federer's progress because of the Swiss star's superior sets record.
The Chilean runs around his backhand when possible, preferring to utilise his often devastating forehand and while that tactic worked occasionally, he looked short of energy as he bowed out.
GOLD GROUP STANDINGS
Ferrer P3 W3 L0 F6 A1 Pts 3
Nadal P3 W2 L1 F5 A3 Pts 2
Gasquet P3 W1 L2 F3 A4 Pts 1
Djokovic P3 W0 L3 F0 A6 Pts 0
Davydenko, who made several unexpected forays to the net, was hardly firing on all cylinders, hitting 33 winners but also making 35 unforced errors.
Gonzalez, however, was even more inconsistent and his frustration was evident when he smashed his racquet after a forehand mistake which saw him lose the first set.
The pattern continued in the second set and although Gonzalez did not lack heart, he was short of inspiration.
A marathon game saw Davydenko break to go 5-3 up and he served out for victory, completing his win with a smash on match point.
"I lost my first two matches but winning the last gives me confidence. Now I can go on holiday," said Davydenko.
"My confidence wasn't so great but I won a few points coming to the net and volleying and I finished strongly."
Spanish duo Nadal and Ferrer booked their semi-final spots with straight-set wins over Novak Djokovic and Richard Gasquet in the Gold Group on Thursday.
ATP Masters Cup, Shanghai, 11-18 November:
Roger Federer (Swi)
Andy Roddick (US)
Nikolay Davydenko (Rus)
Fernando Gonzalez (Chi)
Rafael Nadal (Spa)
Novak Djokovic (Ser)
David Ferrer (Spa)
Richard Gasquet (Fra)