Eugenie Bouchard advanced to the quarter-finals of the Mutua Madrid Open just now, after the top seed, Angelique Kerber, retired during the second set of their match.
Bouchard, who took the first set 6-3, was leading 5-0 in the second set, with Kerber struggling to get momentum going.
Kerber, who was nursing the back of her left leg, eventually called it a day and was visibly upset as she walked off the court.
Kerber will return to the No. 1 WTA position when the new rankings are released next week, following her first round win against Katerina Siniakova of the Czech Republic on Monday.
Bouchard will now play Svetlana Kuznetsova in the quater-finals.