Andrey Rublev overcame illness and losing the first set to beat Felix Auger-Aliassime 4-6 7-5 7-5 for his first Madrid Open title.
The Russian world number eight was under the weather with a fever coming into Sunday’s final and looked out of sorts when he trailed 4-1 in the opening set.
But Rublev fought his way back into the match, striking at the end of both sets to get past the world number 35 and win his second Masters 1,000 tournament.
“I have no words,” Rublev said. “If you knew what I had been through in the past nine days you would not imagine that I would be able to win a title.
“I’m incredibly happy. I have to give full credit to the doctors. They were doing some tricky things and I was at least able to play.
“I would say this is the most proud title of my career. I was almost dead every day. I was not sleeping at night. The last three, four days I didn’t sleep.”
The 26-year-old had lost four consecutive matches before arriving in the Spanish capital but his performance will have encouraged him before the French Open, which starts in three weeks’ time.
Auger-Aliassime, 23, had benefited from the retirement of his semi-final opponent Jiri Lehecka early in their match and the withdrawal of world number two Jannik Sinner with a hip injury before their quarter-final.
The Canadian had to work hard to save break points in the third set where Rublev was the better player, but was eventually undone by a double fault on match point.