Six-time champion Roger Federer reached the last four of the ATP Finals for the 15th time in 16 appearances after defeating Kevin Anderson 6-4 6-3 to top Group Lleyton Hewitt.

As a result of Dominic Thiem’s straight-sets win over Kei Nishikori earlier in the day, South Africa’s Anderson knew he had already qualified for the semi-finals, becoming the first player from his country to qualify for the knockout stages in the history of the tournament.

In an electrifying atmosphere at the O2 Arena, both players were looking ultra-sharp in a rematch of their epic Wimbledon quarter-final, which the 32-year-old won 13-11 in the decider.

Federer applied the squeeze in the seventh game with the Swiss ace breaking through to love as Anderson lost his serve in disappointing fashion for the first time in the tournament.

The 6ft 8in finalist at the All England Club raised his game to hit back in the next though before Federer made it three successive breaks of serve in an amazing turn of events.

Federer played some glorious tennis from 0-40 down to seal the set in style and keep intact his proud record of always reaching the semi-finals at the season-ender since it moved to London in 2009.

Anderson produced a higher percentage of first serves in the second set, which helped him stay ahead of the 37-year-old. That was until Federer pounced to take the one opportunity offered to him in the seventh game. And after holding serve in just 76 seconds, he finished the job off in style with a third break of the Anderson serve to qualify for the last four.