Alexander Zverev of Germany celebrates with the trophy after the singles final against Novak Djokovic of Serbia during Day 8 of the 2018 Nitto ATP World Tour Finals at The O2 Arena in London, Britain on Nov. 18, 2018. Alexander Zverev won 2-0. (Xinhua/Han Yan)

LONDON, Nov. 18 (Xinhua) -- Germany's Alexander Zverev demonstrated his breakthrough in men's tennis by overpowering world No. 1 Novak Djokovic 6-4, 6-3 to claim his first ATP Finals title here on Sunday.

Zverev is the first German player to have triumphed at the season finale since Boris Becker in 1995. He is also the youngest champion of the tournament since Djokovic in 2008.

Djokovic stepped onto the final court without conceding a set, and held all previous service games over the week.

However, following a 4-4 tie in the first set, he was broken for the first time by younger and more energetic Zverev, who utilized three consecutive aces to serve out the set.

Zverev finished another quick break into the second set, before the top seed made his response in the next game. Then the German promise broke again before building a 3-1 lead.

Despite maintaining his next two service games, Djokovic failed to break his German opponent afterwards.

Zverev registered his third break of the set in the ninth game, securing his biggest career title so far with a precise backhand crosscourt.

An emotional Zverev lay on the court of the O2 Arena, before receiving congratulations from his Serbian opponent who gently walked across the net.

"Right now I really can't describe it. I'm unbelievably happy. Obviously it's the biggest title that I've ever won," said Zverev at the awarding ceremony.

Earlier on Sunday, American duo of Mike Bryan and Jack Sock saved one championship point in the match tie-break to edge Frenchmen Pierre-Hugues Herbert and Nicolas Mahut 5-7, 6-1, 13-11 in doubles final, adding the crown to their Wimbledon and the US Open titles.