Novak Djokovic and great rival Roger Federer will clash in a showdown to decide who will reach the last four at the season-ending ATP Finals.
For the vanquished it's campaign over in London.
On Tuesday, Djokovic suffered a 6-7(5-7) 6-3 7-6 (7-5) defeat to an inspired Dominic Thiem in the standout match of the tournament so far while Federer accounted for Matteo Berrettini 7-6 (7-2) 6-3.
The results sealed Thiem's maiden qualification for the semi-finals of the elite eight-man event, ensured a blockbuster meeting between Djokovic and Federer, and ended Berrettini's hopes.
"We go head to head with Roger. Winner goes to semis. Loser doesn't qualify. As simple as that," Djokovic told reporters.
The 49th match between the Serb and Swiss greats will be their first since Djokovic won an epic Wimbledon final in July.
"Actually, it's good for me to play him again, and maybe that all helps to get a chance to get him back," Federer said.
While Federer is trying to avoid only his second group stage exit in 17 appearances at the year-ending showpiece, the stakes will be even higher for Djokovic on Thursday.
Defeat would not only halt his bid to equal Federer's six titles but would also mean he can not equal Pete Sampras's feat of finishing a year ranked No.1 one on six occasions
Djokovic must reach at least the final to overhaul Rafael Nadal.
He will have to recover quickly after being stretched to breaking point by Thiem in a match lasting nearly three hours, in which the Austrian blazed 50 winners in a sensational display of aggressive hitting.
Thiem twice led by a break in the final set and failed to serve out the match at 6-5.
However, he fought back from 4-1 down in the deciding tiebreaker to seal the victory on his second match point.
"I thought he deserved to win," Djokovic said.
He just played very courageous tennis and was just smacking the ball. He went for broke."
Federer was pushed hard by Berrettini in the first set but after the world No.3 claimed 10 of 11 points to breeze through the tiebreaker and break to love at the start of the second his 58th victory at the tournament was never in doubt.
Australian Associated Press
