Roger Federer becomes oldest world no.1 in history Getty Images

Last night, the O2 Arena witnessed Roger Federer put in an amazing performance. The Swiss legend defeated Novak Djokovic and eventually progressed to the semi-finals of the Nitto ATP Finals. The 20-time Grand Slam winner won the match 6-4, 6-3. Federer's win guarantees that Rafael Nadal would finish the year as World No 1.

After completing a magnificent victory over Djokovic, Federer didn't miss the chance to take a subtle shot at his competitor. Federer claimed that the Joker would not have had a chance of becoming year-end number one if the Serb had been beaten at Wimbledon.

It may be remembered that the 38-year-old lost to Djokovic in a hard-fought final at Wimbledon in July. Last night's win means that now Federer would be somewhat relieved to have taken his revenge.

The Swiss produced a superb performance on Thursday, as he dropped just four points on his second serve. Eventually, the Swiss won 78 percent of points on his serve, which frustrated Djokovic.

Roger Federer
Roger Federer

After the match, reporters asked Federer about his views on Nadal's chances of finishing the year as the World Number One.

He said, "I knew there was a lot on the line for Novak today. If he wouldn't have won Wimbledon, maybe he wouldn't have even gotten to that, to be quite honest. That's what I was telling myself, too. Because he beat me at Wimbledon, actually Novak was as close as he was. I'm very happy. I'm very pleased."

Federer now joins Dominic Thiem in the semi-finals from the Bjorn Borg group. On the other hand, Nadal has a difficult task ahead of him as he must win his match against Stefanos Tsitsipas to qualify for the next round.

However, Express reports that a win for the Spaniard won't automatically mean that he will qualify for the semi-finals if Alexander Zverev beats Daniil Medvedev. Since Zverev has won the head-to-head match with Nadal, the former will advance to the next round. Tsitsipas, on the other hand, has already booked his spot in the semi-finals as he beat both Medvedev and Zverev.