Janko Tipsarevic has expressed his frustration at having to retire from this year's Australian Open with a heel injury.
The Serb was 2-6 1-5 down to fourth-round opponent Nicolas Almagro when he was forced to call it a day.
"I don't know how I managed to do it but I completely screwed up my left heel," he said. "I haven't seen the doctor yet and I don't know what he's going to say.
"Nico was playing great tennis, hitting the ball powerfully from both wings. But I was feeling great today, I wasn't feeling tired at all from my previous matches.
"It was a beautiful day for tennis and I really felt I could play well. And I could not be more pissed off with the way I finished the competition."
Tipsarevic has never progressed beyond round four of the Melbourne Grand Slam.
