World tennis number one Roger Federer came from a set down to beat the American Robby Ginepri in the second round of the Cincinnati Masters.
The Swiss, whose four-year reign as the men's No.1 is under threat from Rafael Nadal, closed out the deciding set 6-love.
Now if Nadal wins the tournament and Federer fails to reach the semi-finals, the Spaniard will take over the top spot.
