Mariano Navone has taken the opening set from Novak Djokovic in a first-set tie-break, putting the Argentine within reach of a major upset.
Navone, visibly fired up after edging the tie-break, sensed an opportunity against the Serbian great as Djokovic struggled to impose his authority.
Djokovic must now recover quickly if he is to avoid an early shock, while Navone will attempt to maintain the intensity that earned him the first breakthrough.
