Filip Krajinovic reacts in utter joy after beating John Isner on Saturday to go through to the Paris Masters final. Photo: Michel Euler/AP

PARIS – Serbian qualifier Filip Krajinovic ended John Isner’s hopes of qualifying for the ATP Tour finals when he stunned the American ninth seed 6-4 6-7(2) 7-6(5) to reach the Paris Masters final on Saturday.

The world number 77 was 3-0 down in the deciding-set tiebreak, but he kept his composure to prevail on the first match point, setting up a meeting with either local favourite Julien Benneteau or American Jack Sock.

Isner would have booked his place in the season-ending eight-man event in London from November 12-19 if he had won the title here.

Instead, it will be Sock, the 16th seed, who will make the trip to the 02 Arena if he lifts the trophy in Paris on Sunday.

The last spot is currently held by Spain’s Pablo Carreno Busta.

Isner had his right leg massaged twice by the trainer but it did not prevent him from firing down 31 aces, although it was a perfect service return that gave Krajinovic his first match points, which he converted after two-and-a-half hours.

Krajinovic, who benefited from world number one Rafa Nadal’s withdrawal in the quarter-finals, held serve throughout and relied on his quick backhand to unsettle Isner.

Krajinovic made only four unforced errors in the opening set, saving three break points, and broke on his only opportunity to take a 3-2 lead with a fine service return and closed it out when Isner buried a forehand in the net.

Isner breezed through the second-set tiebreak and he seemed on his way to winning another tiebreaker in the third set when he opened up a 3-0 lead.

Krajinovic had other ideas, though, as he won seven of the nine following points to reach his first ATP final, triggering wild celebrations in his camp.