Monaco — Monte Carlo is not Rafael Nadal's playground anymore, and Novak Djokovic is claiming the throne left vacant by the King of Clay.

For the second time in three years, the top-ranked Serb ended Nadal's run at the clay-court Masters tournament, overcoming a strong challenge from the Spaniard to reach the final with a 6-3, 6-3 win.

Djokovic, who extended his current winning streak to 16 matches, will face sixth-seeded Tomas Berdych as he bids for a second title in the principality after ending Nadal's eight-year reign in 2013.

Djokovic has lost only two matches this year as he reigns over the men's game, raising his hopes that he can knock Nadal off his perch at the French Open, where Djokovic hopes to achieve a career Grand Slam.

"It's hard to say right now. One victory does not change everything that he has achieved on this surface, which is much more than me," Djokovic said. "I still don't think that I am a better player than he is on clay. But I'm obviously trying my best to win all the matches that I play, not just against him but against anybody on any surface. That's the kind of mindset that I have."

With Prince Albert of Monaco among the onlookers, both players produced some stunning tennis as Nadal showed glimpses of his old self, mixing aggression and superb defensive shots.

But the nine-time French Open champion, who is struggling to get back to his best after a wrist injury and an appendectomy, was not consistent enough to deny Djokovic a shot at his fourth Masters title in a row.

"I think I played well for moments," said Nadal. "But I get a little bit tired a little bit too early. Then when you get little bit tired, you play a little bit shorter. Then it is impossible against him. He's phenomenal in the way that he can move the ball to everywhere. If he takes advantage from inside the court, you are dead. "

Nadal rued his missed chances in the seventh game of the opening set, when he was unable to seize the momentum after a stunning forehand down the line that wrongfooted the Serb. Even Djokovic clapped his racket in appreciation.

After Nadal earned a break opportunity, another superb rally followed but this time Djokovic prevailed, smashing a winner following an exchange of lobs.

"That game was very important. I had a breakpoint that he played unbelievable," Nadal said. "It was 63, 63, but it can be much closer. I know that. I think he knows that, too. Everybody knows that."

Nadal went through a bad patch in the next game as he missed an easy backhand to hand Djokovic two break points. He saved the first one but shanked a forehand into the net on the second.

The second set was a tight affair, with Nadal fighting hard to stay in the match, but Djokovic's aggression was finally rewarded after a tense seventh game. Nadal cracked on his forehand to drop his serve and Djokovic broke again in the ninth game to seal his 20th win in 43 matches with Nadal.

"Winning in straight sets against Nadal on this surface, his favorite surface, is a great success," Djokovic said.

It was their first meeting since the Spaniard won his last big title with a win over Djokovic in last year's French Open final.

Djokovic will now try to become the first player to win the first three Masters of the season after back-to-back victories at Indian Wells and Miami. He has an 18-2 record against Berdych, who overwhelmed Gael Monfis 6-1, 6-4 to make it to the final.

But the Czech prevailed the last time they played on clay at the Rome Masters two years ago.

"I think there's always chance," Berdych said. "You just need to try to make yourself as best as you can, try as hard as you can."

Berdych took control from the baseline and Monfils struggled to cope with the fast pace imposed by the big-hitting Czech. Monfils won just 11 points in a lopsided first set before the Frenchman changed his strategy, using more sliced shots to break up his opponent's rhythm. The move paid off early in the second set when Monfils broke back to level at 1-1 as Berdych made two forehand errors.

Monfils failed to build on the momentum, though, dropping his next service game.

After hiring Andy Murray's former coach Dani Vallverdu, Berdych has been in consistent form this year, reaching the semifinals at the Australian Open and finishing runner-up in Doha and Rotterdam.

"I can see the results behind it, which is always very nice and always positive because it hasn't been a quite easy decision to make that (coaching) change in the end of the last year," Berdych said. "I think we (are) going the right way."

Serena wins at Fed Cup 

Nineteen Grand Slam titles. Nearly 20 years as a professional. An undefeated record this year. And not one career loss in the Fed Cup. 

Serena Williams' vast experience proved the difference during an extremely tight first set against Italy's Camila Giorgi in a 7-6 (5), 6-2 win for the United States in a Fed Cup playoff.

Wearing red, white and blue, the top-ranked Williams was put to the test as she kicked off her clay season in front of a hostile crowd Saturday. The end result, though, was quite familiar.

"I competed well," the 33-year-old Williams said. "She played very, very well and I stayed in there. I didn't get negative. I stayed positive and just did the best that I could. I've been working really hard my whole life, so maybe it was just experience."

Neither player broke serve in the first set, which was only decided when Giorgi missed two straight forehands to end the tiebreaker.

"My game is very instinctive and I made two key errors," the 23-year-old Giorgi said. "Two errors are not many but it depends when you commit them. In a tiebreak, two points are worth gold. But I have no regrets for how I played."

Italy's Sara Errani then evened the best-of-five series with the U.S. at 1-1 by routing 57th-ranked Lauren Davis 6-1, 6-2.

Williams improved to 19-0 this year and 15-0 for her career in Fed Cup. The only blemish on Williams' 2015 record came when she withdrew before the Indian Wells semifinals last month with a knee injury.

Giorgi was an unexpected choice by captain Corrado Barazzutti for Italy's second singles spot over Brindisi native Flavia Pennetta but she showed surprising poise and was even able to match Williams' power in the opening set.

Giorgi and Williams had 17 winners apiece in the first set — which lasted more than an hour — while Williams committed 18 unforced errors to Giorgi's 15.

Unable to impose her game, Williams appeared frustrated and kept shouting "Come on!" to herself in angrier and angrier tones as the first set wore on. Williams consistently applauded, putting one hand to her racket, when Giorgi blasted winners by her, prompting the capacity crowd of 4,000 to break into chants of "I-TAL-IA, I-TAL-IA."

But Williams played solidly in the tiebreaker and Giorgi clipped the top of the net on Williams' first set point.

"It was a great match. Giorgi played great throughout," U.S. captain Mary Joe Fernandez said. "Serena did a good job to really fight and play a solid tiebreak. She served really well in the tiebreak, which I thought was the difference."

In the second set, Williams took control early on.

"I haven't played that many points on the clay so I think that factored a little bit," Williams said. "But it was also that she played really well. She had a great game plan and that's the player she is. She just goes for a lot."

Barazzutti was pleased with the score at the end of the first day.

"I hoped it was going to be 1-1 and that's where we're at," he said.

In Sunday's reverse singles, Williams plays Errani followed by Davis against Giorgi, although Barazzutti will likely substitute Pennetta for Giorgi.

The doubles teams named were Christina McHale and Alison Riske against Karin Knapp and Pennetta. But Fernandez has said that Williams will play doubles if the series is tied.

The winner returns to the World Group and can compete for the Fed Cup trophy next year while the loser will be relegated to World Group II.