Wimbledon 2011: Novak Djokovic pays tribute to Tomic effort

World number two Novak Djokovic says his 6-2 3-6 6-3 7-5 victory over Australia's Bernard Tomic was "very difficult".

Djokovic is impressed with the amount of winners and lack of unforced errors the 18-year-old made.

The number two seed will now face Jo-Wilfried Tsonga in Friday's semi-final.