Novak Djokovic says he played his 'worst match of season' after Ferrer loss

World number one Novak Djokovic says his shock defeat to David Ferrer at London's O2 Arena was "the worst match I've played this season".

The Wimbledon champion crashed to a 6-3 6-1 defeat in an hour and 15 minutes, revealing "nothing was going well" and indicating that both tiredness after a long season and feeling unwell contributed to his poor performance.