MIAMI (AFP) — France’s Arthur Fils upset top-seed Alexander Zverev with an outstanding display earning him a 3-6, 6-3, 6-4 win over the German in the fourth round of the Miami Open on Wednesday.

The 20-year-old Frenchman will face 19-year-old Czech Jakub Mensik in the quarterfinals with both players chasing their first Masters 1000 semifinal spot.

Rallying from a set down, Fils showed great determination to fight his way back and go 4-1 up in the second set.

Zverev responded to take a 3-1 lead early in the third but again Fils refused to let the match slip from his grasp.

Fils, using his athleticism and his powerful forehand, broke back to 3-2 and then when Zverev went long on a return took a 4-3 lead.

Zverev held serve to stay in the game at 5-4 down but Fils kept his composure to serve out for one of the biggest wins of his career.

The victory was all the more impressive given that Fils later revealed he was suffering from back pain.

“I was not feeling great in the rallies. I’ve had a little problem in my back since I was young, so sometimes it hurts me a little bit,” Fils explained.

“I had to find a rhythm, (be) more aggressive and come into the court to play my game and not let him play, because when you let him play he is one of the best tennis players in the world. I’m really happy about the way I did it.”

The fourth-round contest was postponed to Wednesday after rain on Tuesday forced a change to the schedule.

Fils had also reached the quarter-finals at Indian Wells earlier this month and he became the first Frenchman to make the Last Eight in both legs of the “Sunshine Double” since Gael Monfils in 2016.

In the opening quarter-final, Bulgarian Grigor Dimitrov battled back from a set down to beat Argentine Francisco Cerundolo 6-7 (6/8), 6-4, 7-6 (7/3) in a riveting duel.

After Cerundolo edged the first, the 33-year-old Dimitrov found his rhythm and was relentless in forcing Cerundolo to work on the baseline for every point.

Cerundolo was 6-5 up in the third set and had one match point but Dimitrov showed his grit again and was able to hold and force the contest to a tie-break.