ATP Finals: Djokovic, Federer to fight it out

Dominic Thiem produced a scintillating display of attacking tennis to beat Novak Djokovic and qualify for the last four at the ATP Finals on Tuesday, leaving the Serbian facing a shootout against Roger Federer. 

In the standout match so far at London's O2 Arena, the Austrian fifth seed took the fight to the world number two, recovering from losing the first set to triumph 6-7 (5/7), 6-3, 7-6 (7/5) Earlier, Federer put himself back in the mix at the end-of-season event with a 7-6 (7/2), 6-3 win against Italian debutant Matteo Berrettini in their round-robin clash. 

Federer and Djokovic will face off on Thursday in a repeat of this year's Wimbledon final to determine who else will progress from Group Bjorn Borg. 

Thiem was forced to play high-stakes tennis against the 16-time Grand Slam winner, taking the breath away with some of his inside-out forehands and single-handed backhands Forced to play at his limit, he hit 50 winners compared with Djokovic's tally of 27 but also racked up 44 unforced errors.