Borna Coric was in disbelief after becoming the lowest ranked player to win an ATP Masters 1000 tournament since 1990 by downing Stefanos Tsitsipas in the Western & Southern Open final.

Coric, who entered the competition ranked 152nd in the world, enjoyed a dream run in Cincinnati as he overcame five consecutive top-20 players, beating Rafael Nadal, Roberto Bautista-Agut, Felix Auger-Aliassime and Cameron Norrie before his win over Tsitsipas.

In the final, the Croatian fought back from 4-1 down to clinch the first set in a tie-break as the world number five crumbled, before cruising to a 7-6 (7-0) 6-2 victory.

And the 25-year-old, who had not featured in a Masters 1000 final since losing to Novak Djokovic in Shanghai in 2018, believes his second-set display was his best of the year.

"It was a very, very tough match. At the beginning I wasn't playing very well and he was pushing me very hard," Coric said.

"But I started to serve better and play better and I was fighting hard. Then in the second set I thought I played the best set of the whole year.

"I didn't believe I was going to win the tournament. I never look too much forward.

"When I was in the semi-finals, obviously I know who I'm going to play in the final, because it's not many matches. But in the first couple of rounds, I'm not really focused on the next round.

"I'm always focused on the round which I'm playing right now. I was just believing that I can win the next match. That's what I did for five days in a row."

For Tsitsipas, the demoralising defeat represented his fourth in six Masters 1000 final appearances, and the Greek was at a loss when attempting to explain his second-set collapse.

"I'm still looking for the answer myself. I don't have a clear answer. He was obviously the opposite of what I was, very much involved," Tsitsipas said.

"Sometimes it makes you not be that much present in the moment when you're too relaxed.

"I think he was serving well. He was making me move a lot. I could have used my chances in the first set. I don't know why I didn't. I rushed a little bit."