London, November 19: Novak Djokovic credited Alexander Zverev for producing a vastly improved display in Sunday's ATP Finals showdown after the German claimed a dazzling victory.
World number one Djokovic was seeking a record-equalling sixth success at the end-of-season tournament, but Zverev prevailed 6-4 6-3 to follow up his semi-final triumph over Roger Federer in style.
When Djokovic and Zverev had met in the group phase in London, the Serbian secured a dominant 6-4 6-1 win.
And the 14-time grand slam winner jokingly conceded he had been met with a far sterner challenge in the final.
"You definitely played much better than in the group stage," Djokovic said in an on-court interview, prompting laughter from the crowd.
"You deserve to win. You are still quite young but you have had an amazing career so far and I wish you all the best for your future.
Alexander Zverev defeats Novak Djokovic to become the #ATPWorldTourFinals champion!— Omnisport (@OmnisportNews) November 18, 2018
The 21-year-old German prevails 6-4 6-3 to deny Djokovic a record-equalling sixth victory at the end-of-season tournament pic.twitter.com/0OfRCjenkg
"Speaking of being young, hopefully I'll play many more years and I will see you guys here in the years to come.
"For that to happen obviously I need a good team, so I want to thank my team for a great season. Obviously today was not a great day for us, but if we put things in perspective it was an amazing year, a great comeback and thank you guys for helping me to get to where I am.
"Last but not least, you fans have made this tournament very special for all of us. Thank you for supporting tennis for 11 months in a year. It's a very long season but you guys make it very enjoyable for all of us and it's a pleasure to perform in front of you."
Djokovic won Wimbledon and the US Open in 2018, as well as Masters 1000 events in Shanghai and Cincinnati.