Rafael Nadal began his Madrid Open title defense with a 6-1, 6-3 victory over Marcos Baghdatis on Wednesday after Novak Djokovic had beaten Kevin Anderson 6-3, 6-4 to win his 30th successive match.
The top-ranked Nadal next plays 2009 U.S. Open champion Juan Martin del Potro, who swept aside Marin Cilic 6-3, 6-0 in 64 minutes.
"I think he's the worst rival to have to face in the second outing of a tournament," Nadal said.
Del Potro, who has dropped down the rankings following a serious wrist injury, wasn't looking forward to playing the five-time French Open champion either.
"The game is going to be of the most difficult you could face on clay, he's at home, playing really very well and hasn't lost on this surface for around two years," Del Potro said.
Nadal broke Baghdatis's serve three times in the first set and once in the second, pinning the Cypriot to the baseline with accurate first serves and precise passing shots.
"It was more or less a comfortable match for me against an always complicated rival, who last time we met beat me," said Nadal who lost to the Cypriot at Cincinnati in August.
The match was watched by Real Madrid star Cristiano Ronaldo, who had flown back to the Spanish capital after playing at Barcelona in the Champions League semifinals on Tuesday.
"I enjoy watching tennis in Madrid and I support the Spanish players a lot," Ronaldo said.
Djokovic's winning streak dates back to Serbia's win in the Davis Cup final last December. This year, he's started 28-0, the best beginning to a season since Ivan Lendl went 29-0 in 1989.
In the next round, Djokovic will play Guillermo Garcia-Lopez of Spain, who has yet to beat the Serb in four meetings.
Djokovic, playing in Madrid for the first time in two years, said the Caja Magica clay courts were very fast, making it hard to control the ball against big servers like Anderson.
The second-ranked Serb was able to break the South African's serve once in each set.
"It's a fact that I am playing the best tennis of my life and I'm definitely happy about it," said Djokovic, who attributed his good form to a "strong mental ability to handle the pressure and play the right shots at the right time."
Third-seeded Tomas Berdych and fifth-seeded Robin Soderling were also winners.
On the women's side, Petra Kvitova of the Czech Republic eased past second-seeded Vera Zvonareva 6-1, 6-4 to reach the quarterfinals.