Jack Sock rallied to stun Marin Cilic 4-6, 3-6, 6-3, 6-4, 6-4 and put the United States on the road to a 2-0 lead over Croatia in their Davis Cup World Group quarter-final tie
The triumph for the 26th-ranked Sock over world number 12 Cilic, the 2014 US Open champion on July 15. 2016 was followed by American John Isner's 6-4, 6-4, 6-3 victory over Borna Coric.
Croatians Ivan Dodig and Marin Draganja are slated to take on the formidable doubles duo of Bob and Mike Bryan brothers today, trying to reverse the singles results on Sunday.
Sock fired 17 aces against Cilic, who came into the tie trying to put behind him a five-set quarter-final loss to Roger Federer at Wimbledon.
But having forced a decisive fifth set, the American surrendered an early break that appeared to set Cilic on his way.
Sock, however, broke back in the fifth game, and while he couldn't convert three break points in the seventh, he gained the last break he needed in the ninth, when Cilic sent a high backhand volley wide.
"A little bit disappointed with that, just to lose that opportunity of getting that lead in the fifth set," Cilic said. "When I gave him a chance to come back I felt that he started to play also really well."
Sock got a little shaky serving it out, double-faulting twice before surviving two break points to seal the match after three hours and 13 minutes.
"I haven't played a ton of five-setters in my career," said Sock, who was playing his first Davis Cup match on home soil.
"Haven't come back from two sets to love down. To do that today, in front of the home crowd for the team, it feels extra special today."
Isner, ranked 16th in the world, fired 23 aces and fended off all eight break points he faced in a match lasting just under two hours.
Having withstood 54th-ranked Coric's early assault on his serve, which included break points in six of Isner's first seven service games, Isner broke the Croatian in the final game of each of the first two sets to take a comfortable lead.
After breaking to lead 3-1 in the third, Isner stayed the course, finishing off the match with a final ace.
"We're up 2-0, we're in a good spot," Isner said.
The winners of the best-of-five match tie will take on either the Czech Republic or France in the semi-finals. The Czechs and French were tied 1-1 after the opening day of their tie in Prague.
