Spain's 10th seed Nicolas Almagro reached his first Australian Open quarter-final after his Serbian opponent Janko Tipsarevic withdrew with a foot injury on Sunday.
Almagro was leading 6-2, 5-1 when Tipsarevic retired to hand the Spaniard a quarter-final match-up against countryman David Ferrer.
Tipsarevic, who was coming off draining back-to-back five-setters, called the trainer to have his left foot bandaged late in the first set before he quit seven games later.
"I was talking with him and he said the problem started at 4-1 in the first set and after that he couldn't move really well and he decided to retired," Almagro said.
"I am not completely happy because Janko was injured. That's not the way you want to win.
"Sometimes you can't do your best and you need to decide to stop if you want to be ready for the next tournament.
"I think he made the best decision if he's really bad and I'm happy to have won a tough match in two sets."
Almagro now must find a way to get past the ultra-consistent fourth seed Ferrer if he is to reach his first semi-final at a Grand Slam.
He has yet to beat Ferrer in 12 encounters.