SHANGHAI — Valentin Vacherot beat his cousin Arthur Rinderknech 4-6, 6-3, 6-3 on Sunday to win the Shanghai Masters for the first title of his career after a stunning run from the qualifying rounds.

The 204th-ranked Vacherot, an unheralded 26-year-old, was the lowest-ranked tournament winner in ATP Masters 1000 history — and the first from the tiny Principality of Monaco.

It was quite a performance too.

He stunned 24-time Grand Slam champion Novak Djokovic in the semifinals to set up a final against the 30-year-old Rinderknech, who had downed four-time major finalist Daniil Medvedev, the 2021 US Open champion, in a remarkable semifinal of his own.

Vacherot produced a serving masterclass in the third set, with three straight love holds and 15 consecutive points before finally losing a point in the eighth game with an unforced error.

Serving to stay in the match at 15-40 down, Rinderknech saved one match point, but Vacherot wrong-footed him with yet another blistering forehand winner down the line to clinch victory.

He held his face in his hands in disbelief before walking to the net to hug his cousin and then rushed to his team box to share a long hug with coach Benjamin Balleret, who is his half-brother and a former tennis player from Monaco.

Balleret’s career highlight was a defeat to tennis great Roger Federer in the early rounds of the Monte Carlo Masters in 2006.

Nineteen years later, Federer was in the Shanghai crowd watching as Rinderknech clinched the first set with an ace.

Vacherot secured an early break in the decider and then missed four break-point chances in the fifth game as Rinderknech got a reprieve. The Frenchman immediately took a three-minute medical timeout for massage treatment on his back and left shoulder.

But there was nothing he could do to stop his cousin’s momentum.

They never played each other before on the professional tour, with Rinderknech winning their only meeting at a futures tournament in 2018.