Djokovic close to peak after walkover victory over Jo-Wilfried Tsonga

Novak Djokovic has warned he is close to reaching his peak after the world number one was handed his third walkover in five matches at the US Open.

Djokovic led Jo-Wilfried Tsonga 6-3 6-2 in Arthur Ashe Stadium when his opponent pulled out with a left knee injury and confirmed the Serb's passage to the semi-finals.