Qualifier Filip Krajinovic stunned John Isner to reach the Paris Masters final and end the American's hopes of qualifying for the ATP Finals.

Isner, a beaten finalist at this ATP 1000 event last year and seeded ninth in the French capital, needed to win Sunday's decider to book his place in the season-ending tournament at London's O2 Arena.

The unheralded Krajinovic had other ideas, though.

The Serbian has shot up the rankings in recent months to 77th in the world, and will continue to climb after defeating Isner 6-4 6-7 (2-7) 7-6 (7-5), as a final against Jack Sock or Julien Benneteau awaits.

Krajinovic received free passage through to his first ATP World Tour semi-final thanks to Rafael Nadal's withdrawal, but he demonstrated his determination by saving three breaks points to hold in his first service game of the match.

Instead it was Isner, seemingly troubled by a knee problem early on, who gave up the only break of a tight opening set to fall behind.

The American then asserted himself in his first meeting with Krajinovic since facing him as teenager on the Challenger Tour in 2008, taking a 5-0 lead in the tie-break before winning the second set and duly levelling the match at 1-1.

The deciding set also stayed on serve but both men showed signs of nerves in the tie-break, Krajinovic giving up a mini break to fall 3-0 down.

Unexpectedly, Isner's booming serve then let the world number 14 down, as he gave up two mini-breaks.

The second of those game when Krajinovic fired off a blistering winner from a return, before holding his own serve to trigger wild celebrations from his coach and fans in the crowd.