He said he was nervous in the first set - he'd lost in the quarterfinals two years in a row - but by the third and fourth sets: "The character on court, the way to win the points ... the level is very positive, much, much better than the end of the season.
"Semifinals is fantastic result for me."
Federer finished his quarterfinal with one of his classic, single-handed backhands in a 6-4, 6-3, 6-2 win over Del Potro, one of only two men who have beaten him in a major final. The other is Nadal, who has done it six times.
That lopsided record aside, there's a touch of extra tension in their usually very cordial rivalry this time, with Nadal telling Spanish reporters during a discussion about player discontent that Federer liked to keep his reputation as a gentleman intact by saying nothing negative in public and letting others "burn."
Both have since played the comments down. On Tuesday, Federer said it didn't damage their relationship.
"No. No. Honestly, no," he said. "It was here for one day and then gone again. I'm happy about that, because it didn't deserve more attention than it did.
"So for me, it's another great match with Rafa ... obviously I'd like to play Rafa because of our great epic match earlier in the finals here a few years ago."
Not a bad appetizer for Thursday. It'll be the first time the pair have met at Melbourne Park since Nadal won the 2009 title in five seesawing sets and collected the trophy from the great Rod Laver, after consoling Federer as he sobbed in the background.
Nadal is expecting a big match.
"The ranking is important, but we are talking about a player who has won 16 Grand Slams, and I've won 10," Nadal said. "We have played a lot of matches together, many in very important moments for our careers. So the matches against him are always special, even if we are (ranked) 20 against 25."
Back in 2009, Federer was aiming to equal Pete Sampras' record of 14 Grand Slam titles and was confident despite entering the Australian Open with the No. 2 ranking.
Nadal had fended off Fernando Verdasco in 5-hour, 14-minute late night semifinal - the longest match at the Australian Open - and said he could barely walk, let alone practice the following day. He'd also had a day less to prepare for the final than a Federer. Despite the odds, he became the first Spaniard to win the Australian title.
Nadal has won 17 of their 26 head-to-head matches overall, including a 7-2 lead in Grand Slam matches. Federer won the last meeting, a 60-minute 6-3, 6-0 demolition at the season-ending championship in November.
It has been almost seven years since the pair last met in the semifinals of a major.
"Yeah, it's been a long time - I don't know when the last time has been when we played in the semis of a slam," said Federer, who is usually an extremely reliable statistician. "Maybe back in 2005, maybe at the French potentially, I don't know."
For the record: Nadal won in four sets against the then No. 1-ranked Federer en route to the title at Roland Garros.
"We have been on opposite sides of the draw many times," Federer said. "I guess it's a nice changeup. OK, it doesn't allow a rematch for the Australian Open final here, you know, but I think it's good for tennis that it changes up a bit."
Nadal certainly didn't want to miss another chance at Federer. He didn't finish last year in good form and has already talked about having time off next month to rest a sore shoulder. He hurt his knee, bizarrely, by sitting in a chair at his hotel on the eve of his first-round match.
Nadal saved four set points in the first set against Berdych, including one with a stunning passing shot on the 29th point of a rally. But Berdych held firm to win the ensuing tiebreaker.
During the tiebreaker, a Berdych shot landed out, and Nadal returned it, then challenged. Chair umpire Carlos Bernardes wouldn't allow it because Nadal hadn't immediately stopped play, but Nadal responded by saying he didn't challenge immediately because he thought the linesman had called it out.
The replay showed the ball was out and Nadal thought the umpire should have overruled.
He didn't win another point in the tiebreaker. In the second set, as Nadal lined up to serve in a key point, a man called out from the crowd: "Come on Rafa, we want a Roger-Rafa semifinal Thursday night."
Nadal obliged.
- AP
