Rafael Nadal returned to his clay-court comfort zone on Wednesday starting his campaign for a fifth Madrid Open title with a 6-4, 6-3 defeat of Steve Johnson.

The victory in 74 minutes lifted Nadal's clay record over Americans to a perfect 10-0 while the third seed improved to 12-3 on the surface this season.

The nine-time French Open champion has four Madrid titles and has played in six finals at his showcase home event.

He is aiming to extend his streak of winning at least one European ATP clay title leading into Roland Garros to 11 straight years.

Nadal goes on to face Italy's Simone Bolelli for a quarter-final spot.

Women's top seed Serena Williams and defending champion Maria Sharapova survived marathon three-setters to reach the quarter-finals.

Williams saved three match points and needed two and three-quarter hours to take her undefeated record this season to 23-0, making the most of a late serving collapse from former number one Victoria Azarenka.

"I could have won, she could have won. I ended up winning and I don't know how," said Williams after her 7-6 (7/5), 3-6, 7-6 (7/1) win. "I feel like it was intense."

"I don't feel like there were a lot of long points, which was weird."

Williams next faces either Ana Ivanovic, the Serbian seventh seed, or Spanish 10th seed Carla Suarez Navarro.

The top seed had found herself in trouble in the third set against Azarenka, who saved a match point in the 10th game to make it 5-5 and then broke for a 6-5 lead.

"Sometimes when you're at that point you have nothing to lose," said Williams. "You just kind of play and hopefully go down with dignity.

"That's kind of how I felt at that point."

Three match points

But Azarenka fell victim to the serving yips, missing on three match points and sending over three double-faults in a row to lose serve and take the match into a deciding tiebreaker.

Williams then raced to five match points, escaping on her first from Azarenka's long forehand return.

Third seed Sharapova went for two and a half hours before seeing off Frenchwoman Caroline Garcia 6-2, 4-6, 7-5.

Sharapova ended the dramatic third-round match with a second-serve ace confirmed from the chair after breaking for 6-5.

Against Sharapova, the 28th-ranked Garcia, clearly peeved to have missed her chance against the five-time Grand Slam winner, gave an abbreviated "drive-by" handshake as the players met for a few quick seconds at the net, following protocol in name only.

"In the third it just came down to a few points, she was the much more aggressive player in the third set; she was going for a lot," said Sharapova.

"Conditions also play a big role, you have a bit of altitude here.

"The ball bounces quite high. Consistency is really important against an opponent that's so aggressive and going for the lines so much."

Sharapova is fighting to regain the number two WTA ranking that she lost last month with an early defeat in Stuttgart and needs to reach the final to have a chance of standing second again behind Williams.

Sharapova is also building for her French Open title defence after beating Simona Halep for the title in Paris last June.

The Russian started 2015 by winning 17 of her first 18 matches, but came to Madrid having lost three in a row.

She has now won 57 of her last 62 matches on clay as she waits to play fifth seed Caroline Wozniacki in the quarters.

Wozniacki advanced over Poland's Agnieszka Radwanska 6-3, 6-2.

Two-time Wimbledon winner Petra Kvitova, the fourth seed, advanced with ease over Russian Anastasia Pavlyuchenkova 6-1, 6-4.

Romanian Irina Begu beat Barbora Strycova 6-4, 6-4 to next take on Kvitova.

Nadal was joined in the third round by sixth seed Tomas Berdych, who accounted for weekend Estoril winner Richard Gasquet 7-6 (7/3), 7-5.

Spanish seventh seed David Ferrer beat Albert Ramos-Vinolas 6-4, 6-0 and Madrid's Fernando Verdasco knocked out US Open champion Marin Cilic 6-7 (5/7), 7-6 (7/5), 6-3.

Bulgarian tenth seed Grigor Dimitrov came back to beat Italian Fabio Fognini 3-6, 6-2, 7-5 while number 12 Frenchman Jo-Wilfried Tsonga beat American Jack Sock 6-3, 1-6, 7-6 (7/4).

John Isner, the 16th seed, fired 23 aces to defeat Brazil's Thomaz Bellucci 7-6 (7/5), 6-7 (11/13), 6-1.