Australian Open 2014: Roger Federer admits 'doubts'

Roger Federer thinks both he and Andy Murray will approach their Australian Open quarter-final clash with "doubts".

Federer, 32, has fallen in the world rankings to sixth following a difficult 2013 where he won just one tournament, while Murray has recently returned to the Tour having been sidelined for four months with a back injury.

The four-time champion, who beat Jo-Wilfried Tsonga in straight sets to secure his spot in the last eight, says he wants to play the "best players" and is relishing the challenge against Murray.