Nikolay Davydenko had no explanation.
Having stood on the brink of a massive Australian Open upset, the Russian collapsed bizarrely from a match-winning position as Roger Federer hammered out an extraordinary quarterfinal win.
Down and almost out, Federer hauled himself off the canvas to win 2-6, 6-3, 6-0, 7-5 after Davydenko held a 3-1 lead in the second set.
Davydenko was blunt in his post-match analysis.
"Everything was s***," he said. "I don't know what has happened at 3-1, second set. I just completely lost everything. I cannot explain what has happened."
Federer, into a semifinal clash with either 2008 winner Novak Djokovic or Frenchman Jo-Wilfried Tsonga, was relieved to have survived.
"(I) was in a tough situation at 6-2, 3-1 down and 15-40 on my serve," Federer said. "I knew I wasn't looking very good, you know. But that's the beauty of best-of-five sets. I wasn't panicking, even though I maybe would have lost the second set had I lost another point there at that stage."
Davydenko will long rue the missed regulation backhand which almost certainly cost him the second set.
Staring at a huge deficit, Federer traded on his unheralded resilience and pluck to reel off 13 games in a row as his Russian opponent self-destructed.
The victory elevated Federer into a record 23rd successive Grand Slam semifinal, measure of the Swiss master's stunning consistency and excellence.
Distracted by a setting sun and Davydenko's lightning start, Federer simply told himself to be patient in the hope a match which seemed lost might eventually be won.
"I've played him (Davydenko) many times and I know he goes through many phases," Federer said. "Some of those phases are a notch under what he can be, so I was hoping for that."
Federer took a leisurely toilet break at the end of a ragged first set, sauntering back on court with the demeanor of a man without a care in the world.
It was a ploy to chew up a little more time as the sun faded from view.
"Of course I'm very happy with the way I played," Federer said. "I hung in there and believed. I got lucky a bit as well."
Davydenko's rollercoaster performance was perplexing.
For a set and a half, he was untouchable, clubbing winners from all over the court. He made Federer look inferior, appearing out of sorts and troubled. In the first set alone, Federer made 17 unforced errors. Once he cleaned up his act, only 33 more unforced errors came from his racquet for the rest of the match.
Faced with the possibility of trailing by two service breaks in the second set, Federer sprang to life.
Suddenly, his serve, forehand and movement clicked. Suddenly, Davydenko began to miss.
And once he had control of the match, Federer was never going to lose. Not even when he failed to serve out the match in the fourth set and twice lost his serve.
Davydenko briefly threatened to take the contest to a fifth set. Truth is he had thrown everything at the winner of 15 majors but could not put away the world No. 1.
Federer is (unfairly) not renowned for his toughness -- mental or physical -- because of the inherent beauty of his stroke-making. But he was outwardly unmoved by the proximity of defeat as Davydenko revelled in blustery, cool conditions.
The Russian broke serve in the first and fifth games of the opening set as Federer struggled to find range. The pattern continued into the second set.
And then Federer awoke with devastating impact.
