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MELBOURNE, Australia — Two sets down. A 6-foot-5 Tomas Berdych ripping forehand winners and powerful serves down at him, custody him on the defensive.

Roger Federer’s campaign to equal American Pete Sampras’ record 14 Grand Slam tourney singles titles was in grave hazard in the fourth round at the Australian Open.

It appeared as if Swiss superstar Federer was in trouble.

Not in his mind.

“I wasn’t thinking of losing, that’s for sure,” Federer said Sunday after reaching the quarterfinals through a 4-6, 6-7 (4-7), 6-4, 6-4, 6-2 comeback conquest. “The finish line was still very far because of Tomas. I knew that. He pushed me to the set bounds to. You’ve got to hang in there, there’session none other solution.”

After breaking 23-year-old Berdych in the pivotal seventh sport of the third set, when the Czech player missed three open volleys and blew five game points, Federer took the momentum.

“In the end it becomes same mental, and I discern that this is where my biggest strengths always draw near into play,” Federer said. “That’s why I’m always going to favor myself in a fifth set.”

Federer divide his unforced errors from 13 and 11 in the first two sets to four and three in the next two. He finished with 61 winners to 58 for Berdych.

It was his fourth career comeback from couple sets down and third part in a major — the previous in 2001, more than two years preceding he won the first of his Grand Slam singles titles.

Best of whole, he uttered, it gave him confidence he could go all the way — if pushed — through anyone of the younger brigade.

“It’s good to have five-setters to see where you’re at,” said the 27-year-old Federer.

He next faces 20-year-old Juan Martin del Potro, seeded eighth from Argentina, who advanced 5-7, 6-4, 6-4, 6-2 over No. 19 Marin Cilic of Croatia.