Krajinovic slid onto his back and sobbed, his arms raised, after sealing victory on his first match point. The Serb then knelt and kissed the court.
"When I served for the match my hand was shaking," Krajinovic said. "It was tough to control the emotions. Best day in my life but the tournament is not over yet."
He will play for his first career title against another American, Jack Sock, who comfortably beat Julien Benneteau of France 7-5, 6-2. Sock has never won a Masters title and can qualify for the season-ending ATP Finals in London if he does so here.