Defending champion Novak Djokovic edged closer to ending 2014 as world No.1 with a comfortable straight sets victory over Stanislas Wawrinka.
Wawrinka stormed into a 2-0 lead but the Wimbledon champion won 12 of the next 14 games to win 6-3 6-0 and stand within a single victory of both the last four at the season-ending tour finals and ending the year top of the ATP rankings.
Just a set in his final round robin match against Tomas Berdych will be enough to reach the semi-final while Wawrinka will face Marin Cilic knowing a win could yet not be sufficient to qualify.
Despite having won 15 of their 18 career meetings, Djokovic had revenge in mind against Wawrinka having lost to the Swiss player in the Australian Open quarter-finals as the No.3 seed claimed his maiden grand slam title.
Tomas Berdych's straight sets win over Marin Cilic had opened the door for Wawrinka to qualify after just two matches and he began seemingly in full appreciation of the circumstances, creating three break points in the opening game before a wide Djokovic backhand secured the breakthrough.
Wawrinka consolidated the early break under intense pressure from Djokovic, who held to love to get on the board and it wasn't long before the Serbian drew level as his opponent sent an errant backhand long.
Djokovic ratcheted up the pressure and broke Wawrinka to love for a second straight service game before claiming a fifth game on the bounce and having won 16 points out of 17, took a firm grip of the opening set.
The world three-time champion could have wrapped up the set but misjudged a net-volley and Wawrinka unleash the perfect response with a rasping backhand on the way to holding serving for just the second time.
The seven-time major champion needed no second invitation to secure the opening set and as cracks began to show in the Wawrinka rearguard, Djokovic stormed into 4-0 lead at the start of the second set with two comfortable early breaks.
The three time champion then cruised to his second group win with the final two games to put himself within one win of finishing the year as world No.1.