(CNN) -- Great tennis rivals Roger Federer and Rafael Nadal will lock horns once again in Saturday's semifinals of the Indian Wells Masters event in California.
Federer, seeking to reach the final for the first time since 2006 when he won it for the third year in a row, was first into the last four as he added another milestone to his illustrious CV.
The former world No. 1 thrashed ninth seed Juan Martin del Potro 6-3 6-2 on Friday to become the first man to win 250 matches in Masters 1000 level tournaments.
Last year's runner-up Nadal then overcame another Argentine -- former world No. 3 David Nalbandian -- despite dropping his first set of the U.S. hard-court event in a 4-6 7-5 6-4 victory.
"They're always special matches, especially because they're always in very important matches for both of us," said Nadal, who beat Federer in the Australian Open semifinals in January to move 18-9 ahead in career meetings.
"That always makes the match very special. But even if it's not the final, being in the semifinals is an important match.
"Playing against Roger always means a little bit more than against the rest of the opponents because I am playing probably against the best of the history, and because I played probably the most important matches of my career against him and probably him against me. That's why it makes the match a little bit more special than the rest."
Federer and Del Potro were both seeking their 20th victories of this year, but the 16-time grand slam champion comfortably won for the fourth time in 2012 against the man who beat him in the 2009 U.S. Open final.
"I sort of expected myself to come out and play a good match today after the struggle I had against Thomaz Bellucci," the 30-year-old said.
"I don't usually struggle back-to-back days, so this was for me a really good match against a great player. I'm happy I was able to maintain the great streak I've got going against him this year."
Federer has won 37 of his last 39 matches, the other loss coming to John Isner in the Davis Cup while playing for Switzerland.
Home hope Isner plays defending champion and world No. 1 Novak Djokovic in the first of Saturday's semifinals.
He is bidding to become the first American ATP Tour player to triumph in the Palm Desert since Andre Agassi in 2001. But the 26-year-old is 0-2 against Australian Open champion Djokovic.
Meanwhile, top-ranked Victoria Azarenka will play world No. 2 Maria Sharapova in Sunday's women's final in Indian Wells.
Azarenka extended her unbeaten run to 22 matches, surpassing Serena Williams' start to 2003, as she beat German 18th seed Angelique Kerber 6-4 6-3 to claim the best beginning to a campaign since Martina Hingis went 37-0 in 1997.
"I'm really impressed by the way Angelique was playing," Azarenka said of her opponent, who has reached seven semifinals in her last 11 events.
"It was the first time we played on the pro tour, so it was a little bit new for me, and she showed some excellent tennis. I think she's a great player and she really pushed me to raise my level and really dig to win that match."
Sharapova, the 2006 champion in Indian Wells, had easier progress to the final as her opponent -- fellow former No. 1 Ana Ivanovic -- retired with a hip injury while trailing 6-4 0-1.
Ivanovic won the tournament in 2008 and was runner-up the following year, but the Serbian has slipped to 16th in the rankings.
"I started to feel it in the middle of the first set," she said. "It just got gradually worse and worse. I started to feel a lot of pain through my glute and couldn't load on my backhand side.
"After the treatment it was getting worse and worse rapidly. We taped it and I tried to continue, but I couldn't even stand there on my return."
Sharapova lost to Azarenka in January's Australian Open final, and the Russian will be seeking to prevent her Belorussian rival from winning a fourth title in 2012.
"She's definitely the one to beat right now, someone that's playing with a lot of confidence and all the momentum in the world," Sharapova said.
"I'd love to get my revenge from Australia and play much better, as well. In our previous meetings we had really tough matches and I hope the quality of tennis will be good and hopefully I can change a few things around this time."