Spain's Rafael Nadal looks at his coach during a training session at the Barcelona Open tennis tournament, April 18, 2011.  [Photo/Agencies]

MADRID - Rafa Nadal said he must try to keep improving his game after securing a seventh straight Monte Carlo Masters title at the weekend.

The world number one beat fellow Spaniard David Ferrer 6-4 7-5 in Sunday's final but explained he was still a little rusty on clay, his favourite surface.

"I'm pleased with how the first week (on clay) has gone," Nadal told a news conference at the Barcelona Open on Monday.

"I need to use the confidence from the first week to keep improving. I have to be more aggressive, to serve better and to finish off points more emphatically and with more authority."

After Barcelona, Nadal will compete in Madrid, Rome and then at the French Open in Paris, giving him three possible chances of a clash with in-form Serb Novak Djokovic.

The world number two has won 24 successive matches in 2011, including final victories over Nadal at Indian Wells and Miami, and a claycourt showdown between the two is eagerly anticipated.

It was put to Nadal that Djokovic rather than Roger Federer was now his main rival for the number one spot.

"He (Djokovic) has started very well and I congratulate him," said the five-times French Open champion.

"Roger and I have played many important matches, with great moments for each of us. The year is very long and he (Djokovic) is in a privileged position but unfortunately I have to worry about many others as well.

"I'm not invincible on clay. I have lost before and unfortunately I have plenty more games I will lose in the future. It has gone well for me in recent years but no one is perfect."