Federer focuses on fitness, not rankings

Roger Federer's impressive return from injury has prompted talk of his possible return to number one in the world, but the 18-time Grand Slam winner says looking after his body is far more important than chasing the rankings positions.

Since coming back from a six month injury lay off, Federer has won the Australian Open and Indian Wells this year and on Monday cruised past Juan Martin del Potro to move into the fourth round of the Miami Open.