Marin Cilic's US Open victory could be the first of many Grand Slam titles, says his coach Goran Ivanisevic.
Cilic, 25, beat Kei Nishikori 6-3 6-3 6-3 to become Croatia's first major champion since Ivanisevic at Wimbledon in 2001.
"He can win more Grand Slams," Ivanisevic, who began working with Cilic last year, told BBC Sport.
"It's unbelievable, it's amazing. I'm so proud of him, that he was able to play the final like this."
World number 16 Cilic completed a superb run at Flushing Meadows that saw him win his last 10 sets, including straight-sets victories over sixth seed Tomas Berdych, five-time champion Roger Federer and 10th seed Nishikori.
|BBC Sport tennis correspondent Russell Fuller|
|"This time last year Marin Cilic was holed up in Croatia, serving the last few months of his doping ban and adding a few more revs to his serve. The burning sense of injustice he still feels has driven him to an achievement which had appeared beyond him; he played so calmly and consistently for most of the match - as if the trophy was his destiny.|
|"Coach Goran Ivanisevic has also played a major part, adding more shots to his repertoire and inflating his self-belief. The faster courts at the US Open played to his strengths, and he will enjoy Australia too... when the Grand Slam year restarts."|
He is the lowest-ranked player to win a Grand Slam since Argentina's Gaston Gaudio won the 2004 French Open as the world number 44.
Arguably most impressive was the way Cilic kept his nerve and maintained his form against another Grand Slam final debutant in Nishikori, with such a huge prize on offer.
"I said whoever was able to overcome the nerves is going to win the tournament and that's what happened," said Ivanisevic.
"After the first couple of games there was only one player on the court and that was Marin. Nishikori could not cope with him in any aspect of tennis.
"The last 10 sets were the 10 best sets of his life. After this, he doesn't need to play any more sets!"
Cilic did not play at last year's US Open because he was serving a ban, reduced on appeal to four months, for taking a banned stimulant.
The player claimed he did so inadvertently, but during his absence from the game he teamed up Ivanisevic and began working to improve his serve and his forehand in particular.
|Marin Cilic's path to victory|
|First round: Beat Marcos Baghdatis (Cyp) 6-3 3-1 - retired|
|Second round: Beat Illya Marchenko (Ukr) 7-6 (7-2) 6-2 6-4|
|Third round: Beat Kevin Anderson (SA x18) 6-3 3-6 6-3 6-4|
|Fourth round: Beat Gilles Simon (Fra x26) 5-7 7-6 (7-3) 6-4 3-6 6-3|
|Quarter-finals: Beat Tomas Berdych (Cze x6) 6-2 6-4 7-6 (7-4)|
|Semi-finals: Beat Roger Federer (Swi x2) 6-3 6-4 6-4|
|Final: Beat Kei Nishikori (Jpn x10) 6-3 6-3 6-3|
"This is his second chance," said Ivanisevic. "He took it, he deserves it and now anything can happen. This guy, when he plays like this - this is real tennis.
"It was not an easy year and it came in the perfect, perfect moment. From this he can only go up and up. His life is never going to be the same again.
"He's the nicest guy and deserves it. And as a coach - now I can resign! I won a Grand Slam as a coach."
Cilic will climb from 16th to ninth in the world rankings and has all but guaranteed his place at the ATP World Tour Finals in November.
On Ivanisevic, he said: "Goran is a great guy. You get to know him and he has a huge heart. Anyone who asks him for help, he's going to help in one way or the other. That's the way he is."
Asked about Ivanisevic's famous claim after he won Wimbledon that there were "three Gorans", Cilic replied: "With personalities, I think he has only one, and that's with a very big heart."