Rafael Nadal described 20-year-old Alexander “Sascha” Zverev as an “unbelievable player” following the German’s latest triumph in Montreal over Roger Federer.

Zverev, the current world No. 7, captured his second Masters 1000 title of the season in Canada last Sunday, to rise to the third position in the Race to London, where he stands behind Nadal and Federer.

The German youngster has made waves in 2017, claiming a tour-leading five titles and enters Cincinnati carrying a 10-match winning streak.

Nadal is 3-0 against Zverev, and needed a deciding set in two of those encounters to come through at the Australian Open this year and in Indian Wells last season.

Both Zverev and Austria’s Dominic Thiem, who is 23, have separated themselves from the younger generation and have established themselves as top-10 players ready to challenge the top guns.

While Thiem has had better results at the majors than Zverev, reaching the semi-finals at Roland Garros in 2016 and 2017, the world No. 8 is somehow being overshadowed by the German, who has had big results on all three surfaces.

“When you already talking about a player that already won two Masters 1000 in the same year, you’re talking about an unbelievable player,” Nadal said of Zverev in Cincinnati.

“And Dominic is there too. It’s true that he didn’t win (a big title) yet but he already played two Grand Slam semi-finals, and he lost the final against me in Madrid, that was close.

“Both are so good. It’s true that Zverev is younger but it’s true that Dominic is probably a bit better on clay and Zverev is better on faster surfaces. But most of the year we are playing on faster surfaces.”

Six of Thiem’s eight titles have come on clay and he is 5-5 win-loss since the start of the grass season.

Thiem opens his Cincy campaign against Italian Fabio Fognini on Wednesday while Zverev takes on American teen Frances Tiafoe.