World No 1 Novak Djokovic
showed his class late on Friday night as he held his nerve against Marin Cilic to boost his chances of winning the Nitto ATP Finals in London
with a 7-6, 6-2 win.
The two players traded blows in a first set that had to be settled by a tie-break before Djokovic took control of the contest in a bid to conserve his energy with a straightforward second set.
Djokovic has little time to recover as he takes on big-hitting South African Kevin Anderson in Saturday's semi-finals but he goes into the business end of the competition as the only player to remain unbeaten.
'Obviously I knew before the match that I had already qualified, and I knew who I'm playing, so it wasn't easy to approach this match with 100 per cent willingness to win it,' said Djokovic.
'But this is a unique format and both of us wanted to win from the first point. It was a close first set which probably decided the match.
'(Anderson) is playing some great tennis, it's definitely his best season and he's continued doing that throughout this tournament.
'He's playing well, serving well, very aggressive, so I know what to expect.'
Djokovic has enjoyed a fine renaissance in the last six months taking both the Wimbledon and US Open titles.
He heads into the final weekend in London favourite to lift the title with Roger Federer expected to be his opponent in the final - should he overcome 21-year-old Alexander Zverev in the first semi-final.
His opponent on Saturday night is Kevin Anderson who has impressed on his maiden appearance at the Finals in London.
Victories over Dominic Thiem and Kei Nishikori show his confidence following an impressive season - but in the last eight matches, Anderson has only beaten Djokovic once and that came 10 years ago in Miami.