The third-seeded Nadal , a 14-time Grand Slam singles champion, said before the tournament began that his lack of match fitness because of injuries and illness in the last half of 2014 made him unlikely to win more than a few rounds at Melbourne Park.
Nadal saved two match points in the 12th game of the final set, sending it to a tiebreaker. Berdych led 5-2 and finally ended the match on his fourth match point when Nadal netted a return of serve. Coming into the Australian Open, Nadal had played only eight matches since last June because of a right wrist injury and appendix surgery in November.
In the women's singles, Maria Sharapova moved closer to another Australian Open title, set to face a fellow Russian in the semifinals who has never beaten her.
Sharapova made all the big points look easy Tuesday in defeating 20-year-old Eugenie Bouchard, 6-3, 6-2 — her fourth consecutive win over the Canadian — and advance to a semifinal against Ekaterina Makarova, who earlier beat third-seeded Simona Halep, 6-4, 6-0.
"I had to produce a really good performance against Genie," Sharapova said. "She's been playing so confidently and aggressively."
The last time Sharapova and Bouchard met — in the semifinals at the French Open last year — Bouchard won the first set before Sharapova came back to take the next two. Sharapova then won the title at Roland Garros.
This time, Bouchard, who made the finals of Wimbledon and two other Grand Slam semis last year, didn't come close to taking a set, looking flat from the outset while being broken in her opening service game.
Sharapova, the 2008 Australian Open champion, has a 5-0 record against Makarova, including wins in the quarterfinals here in 2012 and 2013. In four of those losses, Makarova failed to win a set.
"She likes playing here," Sharapova said of Makarova. "She uses that left-handed serve really well. It's always tricky playing a lefty and your compatriot, as well, but one of us will be in the final, and that makes me happy."
The other women's semifinalists will be determined on Wednesday when No. 1-ranked Serena Williams plays last year's finalist, Dominika Cibulkova, and Venus Williams, 34, playing in her first Grand Slam quarterfinal in nearly five years, takes on 19-year-old American Madison Keys.
If the Williams sisters play each other in the semifinals, it would be their first meeting in a Grand Slam tournament since the Wimbledon final in 2009 — won by Serena.