Marin Cilic has admitted that he is in disbelief after winning his maiden Grand Slam title at the US Open.

The 25-year-old thrashed Kei Nishikori in straight sets at Flushing Meadows to become the first Croatian to win a major since his coach Goran Ivanisevic in 2002.

Cilic missed last year's US Open as he served a ban for taking a prohibited substance, and the world number 15 has confessed that he cannot believe how far he has come over the past 12 months.

"I don't know how I did it. It was hard work over the last few years and especially this last year," Cilic told reporters. "My team has brought something to me, especially Goran.

"We're all working really hard but the most important thing he brought to me was enjoying tennis, and always having fun. I think I played the best tennis of my life."

Cilic also beat Tomas Berdych and 17-time major champion Roger Federer on his way to victory in New York.