(CNN) -- Big-serving American John Isner stands between world No. 1 Novak Djokovic and his fourth final appearance in six years at the Indian Wells Masters 1000 event in California.
Defending champion Novak Djokovic booked his berth in Saturday's semis with a 6-3 6-4 win over Spanish 12th seed Nicolas Almagro, while No. 11 Isner overcame Frenchman Gilles Simon.
The Serbian recorded his 10th successive win at the U.S. hard-court tournament, which he also won in 2008 and was runner-up the year before.
"I had a very powerful ball striker on the opposite side of the net," the five-time grand slam winner said.
"He's very solid from groundstrokes and has a powerful serve, but I knew that he's inconsistent with that, so I just needed to hang in there, which I did."
Djokovic, who beat Rafael Nadal in last year's final and also in an epic Australian Open title match in January, was pleased with his performance against the Spaniard's compatriot.
"It's definitely satisfying to play well," he said. "This is something that we all want to do, and we all practice very hard each day in order to play as best as we can in the official matches.
"At this stage of the tournament it was important for me to stay mentally focused from the first to the last point."
Isner reached the last four with a battling 6-3 1-6 7-5 victory over 13th seed Simon.
"It's pretty satisfying," said the 26-year-old, seeking to become the event's first U.S. winner since Andre Agassi in 2001.
"I don't feel like I played my best. I don't think Gilles did, either. So we're both kind of fighting that the whole match. My coach said it wasn't a Picasso out there, but I found a way to get it done."
Second seed Nadal faces former world No. 3 David Nalbandian in Friday's quarterfinals following three-time champion Roger Federer's clash with another Argentine, ninth seed Juan Martin del Potro.
In the women's draw, former world No. 1s Maria Sharapova and Ana Ivanovic will square off on Friday for the first time since the 2008 Australian Open final for a place in the Indian Wells title match.
Second seed Sharapova, who missed out on a return to the top of the rankings when she lost to current No. 1 Victoria Azarenka in January's Melbourne final, survived a spirited fightback from fellow Russian Maria Kirilenko.
Azarenka takes on German 18th seed Angelique Kerber in Friday's opening semifinal.
Sharapova was one set and a break up on her 20th-seeded opponent, but Kirilenko rallied before eventually losing 3-6 7-5 6-2 to the 2006 Indian Wells champion in a match lasting over three hours.
"She controlled most of the points and I was on the defense a lot which created so many opportunities for her, and she gained a lot of confidence," the three-time grand slam winner said.
"When she took the break in the second set I was still just trying to find my rhythm. It was a little bit of everything, movement and playing-wise, but I started feeling better. Towards the end I really got my by groove back."
Ivanovic, the 2008 Indian Wells winner, beat French seventh seed Marion Bartoli 6-3 6-4 in their quarterfinal.
"Has it been that long? It's actually pretty amazing," the Serbian said of her last clash with Sharapova, which was the 2008 French Open winner's first grand slam final.
"She definitely still has the same style, really aggressive and goes for that first serve, and she obviously has a big serve.
"I think that has improved as well. It's going to be tough, but I want to focus on what I'm doing."