Classy Alexander Zverev clinches three-set win over Marin Cilic
Alexander Zverev beat Marin Cilic in a tight three-set match during the group stages of the ATP World Tour finals in London.
The German took the first set 6-4 but looked to be struggling as he conceded the next 6-3.
However, Zverev then played some sensational tennis, in his first appearance at the event, to take the final set 6-4.
The world number three, aged 20 and the youngest qualifier for the season-ender for nine years, appeared to be fading after a dazzling start, but surged back in style.
With Cilic serving to stay in the match he produced a stunning backhand winner to earn three match points and needed only one of them, crunching away an easy volley to win.
Defeat left Croatian Cilic, beaten in this year's Wimbledon final by Roger Federer, with a miserable 1-6 career record in the London season-ender.
Zverev, bidding to become the first German to finish the year in the world's top three since Boris Becker in 1994, will face a mouthwatering clash with Federer on Tuesday.
Six-times champion Federer earlier had a comfortable win over Jack Sock.
Additional reporting: Reuters