The tennis world number two Roger Federer is in a confident mood heading into tonight's Australian Open quarter-final showdown with this month's Heineken Open winner Juan Martin Del Potro.
The Swiss says his mental toughness is his biggest strength and that was fine tuned by yesterday's five set win, achieved after being down two sets.
However, Federer says last year's end of season form is anything to go by Del Potro will be a dangerous opponent.
Meanwhile, defending champion Novak Djokovic meets seventh seed Andy Roddick in today's other men's quarter final.
