KEY BISCAYNE, Fla. (AP) -- The previous two matchups between Serena Williams and Simona Halep were blowouts.

This one was a thriller.

Williams is making another trip to the Miami Open women's final after beating Halep 6-2, 4-6, 7-5 in a 2-hour, 7-minute classic on Thursday night. Looking for her eighth title at Key Biscayne, the top-seeded Williams meets 12th-seeded Carla Suarez Navarro of Spain on Saturday.

''I made so many errors and I was like `Serena, just come to the net at this point, because that's the only thing that was working for me,''' Williams said. ''I'm just really happy to get through that. It was actually a really fun match and I was able to come out and play here tonight.''

Halep, the No. 3 seed from Romania, beat Williams 6-0, 6-2 last year during round-robin play at the WTA Finals. Williams returned the favor later in that tournament, 6-3, 6-0. They were to meet in the semifinals at Indian Wells last month, but a balky right knee forced Williams out of that matchup.

The knee wasn't a problem in this one. Halep was, but as is usually the case, Williams found a way. She had 38 winners to Halep's 10, overcoming 45 unforced errors and saying afterward that she feels like some practice time is necessary.

''Keep trying, that's all I could do,'' Williams said. ''I never gave up.''

Williams is 4-0 all-time against Suarez Navarro, who's assured of reaching the Top 10 in the world rankings win or lose.

The win also means Williams will extend her reign atop the rankings to at least 116 weeks, which passes Chris Evert's 113-week run for third-longest in WTA history. Only Steffi Graf (186) and Martina Navratilova (156) have been there longer in succession.

''I was close,'' Halep said. ''I saw that I can win against her. ... She was better.''

Suarez Navarro got her finals ticket after topping Andrea Petkovic 6-3, 6-3 earlier Thursday.

''It's a really important tournament for me,'' said Suarez Navarro, the first Spanish woman to make the final at Key Biscayne since Arantxa Sanchez-Vicario in 1993. ''I just practice all day, all the time during the offseason to play in a final like this.''

Williams isn't the only American still alive at Key Biscayne. No. 22 seed John Isner became the first U.S. man to reach the semifinals there since Mardy Fish in 2011, downing fourth-seeded Kei Nishikori of Japan 6-4, 6-3.

Next up for Isner: World No. 1 Novak Djokovic, the four-time champion at Key Biscayne who beat Spain's David Ferrer 7-5, 7-5 in another quarterfinal.

''I played extremely well today,'' Isner said after winning in just 1 hour, 10 minutes. ''I needed to play well in order to beat a player like Kei and that's what I did. From start to finish, I felt like I was aggressive. I was playing all the right shots and things just went my way.''

Isner correctly picked Final Four on his NCAA Tournament bracket. He's now in his own Final Four.

Isner was serving at 4-4, 0-30 in the first set, briefly flirting with trouble. A few minutes later, it was basically over. He won the next 11 points and 19 of the next 21, at one point leaving Nishikori with no choice but to shrug his shoulders as another winner whizzed past.

Isner has not been broken in the tournament and won 41 of 52 points on his serve Thursday with 13 aces.

''Serve, I didn't have any chance,'' said Nishikori, the Japanese star who stands 5-foot-10, a foot shorter than Isner.

Djokovic got on a similar roll in his quarterfinal. Down 3-0 early, he won 10 of the next 13 games and never looked back - spoiling Ferrer's 33rd birthday.

''A very close match,'' Djokovic said. ''I enjoyed it.''

Up 4-2 in the opening set but facing break point, Ferrer stabbed his racket out to snare a passing try by Djokovic, the resulting drop-shot winner drawing raves from the crowd and even a racket-clap from Djokovic himself.

It was one of the last hurrahs for Ferrer.

Djokovic got the break two points later, putting the opening set back on serve. Another break followed for a 6-5 lead, and Djokovic finished the 58-minute opening set off with a hold.

It was the 31st time he's won a first set at Key Biscayne. He's now 31-0 in those matches. Ferrer fought off a match point and ended up breaking Djokovic to knot the second set at 5-5, then lost eight of the match's remaining 10 points.

''I expected it to be a very physical match as it always is with David,'' Djokovic said. ''He's one of the greatest competitors out there.''