Sock downs Zverev to make Tour Finals semi-finals
London: Jack Sock booked a place in the semi-finals of the ATP Finals with a surprise 6-4, 1-6, 6-4 win over German prodigy Alexander Zverev, while title favourite Roger Federer warmed up for the last four by subduing Marin Cilic.
Sock is the first American to reach the semi-finals of the season-ending event since Andy Roddick in 2007. The 25-year-old, up to a career high ninth in the world rankings, only qualified for the Tour Finals thanks to his first Masters title in Paris earlier this month.
Sock was so sure he wouldn't make it to the O2 Arena that he had planned to play a round of golf at Augusta this week.
Instead of working on his putting, Sock ground out a hard-fought victory over third seed Zverev, securing second place behind Federer in the Boris Becker group and a Saturday semi-final date with Pete Sampras group winner Grigor Dimitrov.
"That was a rollercoaster match. I didn't have the hottest start in the third but I kept in there and kept fighting," Sock said.
Dimitrov, who takes on Pablo Carreno Busta on Friday, qualified for the last four after winning his first two matches.
Federer's opponent will be either Belgian David Goffin or Austria's Dominic Thiem, who clash in a winner-takes-all Sampras group tie on Friday.
Just four months ago and only a few miles across south London, Federer was celebrating his record eighth Wimbledon crown after crushing Cilic in a brutally one-sided final.
Cilic had been hampered by a blistered foot and the Croat was reduced to tears during the match as his predicament sunk in.
In their first meeting since that All England Club showdown, Federer frustrated the already eliminated Cilic once again as he fought back to win 6-7 (5/7), 6-4, 6-1.