Novak Djokovic holds off Milos Raonic challenge to edge second ATP win

The reigning champion survived some intense pressure in a high calibre showdown to claim a hard-fought 7-6 7-6 triumph after more than two hours of pulsating tennis.

Raonic will rue a series of missed chances as his poor record against the world number two continued, despite an attacking performance that showed just why he made his first major final at Wimbledon earlier this year.

He will now meet Dominic Thiem on Thursday in what is a straight shoot out to join Djokovic in the semi-finals.

Twelve-time Grand Slam winner, Djokovic will be hugely relieved to have dug out the victory with the added bonus of qualifying prior to his final round-robin game against Gael Monfils.

He is now one step closer to his dual aim of a fifth straight-end of-season title and a return to the top of the rankings, though he'll need to cut out some of the surprising errors that saw him broken back twice and save a set point in the latter stages of the match.

The Serbian came into his eighth meeting with Raonic boasting a 100 per cent record, but his travails over the past six months coupled with his younger opponent's emergence as a real contender for the major prizes, had many suggesting this could be the Canadian's night.

Raonic added credence to this belief as he started the match all guns blazing, but he couldn't convert a trio of early break points as Djokovic clung on in his first two service games. The 'Djoker' needed all of his famed elasticity and ability to turn defence into attack throughout a superb first set in which Raonic unloaded a series of forehand winners and crunching serves.

It looked like he may finally end a run of losing 14 straight sets against the Serbian in the tie break, but fell apart when he missed a backhand volley at 3-1 up. Djokovic stormed back and shaded it 8-6.

Raonic must have felt it was a case of same old story and he was broken for the first time at the start of the second as the reigning champion went for the kill.

To his credit, the Canadian kept attacking and refused to go away, breaking back twice to lead 5-4. Raonic then had a set point at 6-5 on the Djokovic serve but smoked a forehand attempt into the net.

The second set tie-break followed a similar pattern to the first, with Raonic seizing the initiative but struggling to pull clear. Djokovic took full advantage and after serving an ace he forced the error from his opponent to claim the tie break 7-5 and come through a major test.