Marin Cilic attributed his stunning renaissance at the French Open to 'serving fantastically well' after he moved into the semi-finals.
The 33 year old won an absolute epic against Andrey Rublev on Wednesday, winning 10-2 in a super-tiebreak after they could not be separated after five sets of tennis.
Cilic's performance at Roland Garros this year has been a genuine surprise after he has suffered a few years of frustrating decline.
However, he now looks to be a genuine contender to win the title as long as he can hold his level for two more matches.
"I'm unbelievably proud," Cilic told Eurosport after his 5-7, 6-3, 6-4, 3-6, 7-6 epic.
"Today was a tough day in the office and playing against Andrey is really a tough thing to do. Today was slightly different conditions to two days ago.
"It was a little bit harder in that the ball was not bouncing as much. Then it was not easy to open up the court and use the top spin. Luckily today I was serving fantastically well.
"I kept my focus today. It was not easy after losing that fourth set. He was really close to breaking a couple of games but I just kept my head down and put it in.
It is a surprise, yet hugely welcome return to form from Cilic, who was a regular contender for Grand Slam titles a few years ago.
Those peak years produced one major title, the US Open, and also saw him reach the final at both Wimbledon and the Australian Open.
"I had some flashes in the last several years. A few years when I was playing incredibly well, aged 17 and 18, was incredible. I connect three, four sets but never this much in a tournament.
"I'm just trying to be myself in the court and whatever I feel on the court I just go for it.
"I'm just enjoying myself on the court and this performance and the fight. Andrey on a few occasions showed great sportsmanship and in this kind of a match every single point counts. I have to hand it to him.
"Bad luck to him, unfortunately one of us had to go down but it just shows he's an incredible guy and an incredible player."
Cilic will play Casper Ruud in the semi-final on Friday with the Norwegian chasing his maiden major.