Novak Djokovic is not a machine, says Philipp Kohlschreiber's coach

The coach commented on Alexander Zverevs ATP Finals and the way Novak Djokovic ended his season, with two losses in Paris Masters and London finals respectively against Karen Khachanov and the 21-year-old German.

Summerer is not surprised about Zverevs success: Sascha was already a top player in the last years. Probably he did not get far in the Grand Slams, but he already won some 1000s, beating good opponents, Summerer told TennisNet.

What surprised in London: Sascha served unbelievably well. And when he serves so well, he is on fire. He makes less unforced errors, plays aggressively on the forehand side and the serve is clearly a weapon. Summerer thinks Djokovic is the favourite at the 2019 Australian Open, but at the same time, he added: Every player is vulnerable.

, even if he played at an unbelievable level until the match against Khachanov. He is difficult to beat. But I think there are opportunities also for other players. This years ATP Finals featured a lot of straight-set matches and several players did not compete at their best level, which does not surprise Summerer: Looking at the results, it was a bit strange.

Of course, all the players were tired. If one player has a good day, the other one has a bad day, then a match can quickly change. Especially at the end of the season, where you could be mentally tired. ALSO READ: Rafael Nadal: Worse players than David Ferrer won a Grand Slam title