MELBOURNE, Australia — The end came all at once for Rafael Nadal, and then it happened slowly.
Down one set and on the ropes against Mackenzie McDonald in the second round of the Australian Open on Wednesday, Nadal injured his hip while chasing down a shot in the eighth game of the second set. His eyes, filled with concern, immediately turned to his coaches seated courtside at Rod Laver Arena. He then crouched in the corner to catch his breath. Moments later, he returned to continue, because for Nadal, the one thing worse than losing is quitting.
Knowing his day and his tournament were all but done, he watched two aces blaze by, bringing him to the brink of going down two-sets-to-love against McDonald, a 27-year-old American who has never cracked the top 40 in the world rankings. McDonald had played the match of his life for nearly two sets, then did what he needed to do to close out…