After three Grand Slams and two-and-a-half years ranked No 2, it's easy to forget Rafael Nadal is only 21.

But with persistent knee tendinitis and a sticky start to the Masters Cup, age may already be catching up with him.

"I'm only 21 years old. But it's my third time here and sometimes people think I'm very old," Nadal said.

"So I have to continue to improve."

The Spaniard had a taste of his own medicine late on Tuesday from compatriot David Ferrer, who out-ran and out-hustled the Mallorcan in three high-energy sets.

Despite wearing strapping on both knees and slowing in the final set, Nadal insisted he was injury-free.

"No physical problems, no. Everything's fine," he said. "It was a tough match, we ran a lot, so I was a little bit tired. That's it."

But Nadal's all-action style has long provoked concern over how long he can last at the top of the sport.

"He's writing checks you hope his body can cash," Andre Agassi said at the 2005 Masters, days before Nadal pulled out injured.

Nadal enjoyed a successful first half of the season, winning his third French Open and making his second Wimbledon final after reach an Open-era record of 81 consecutive wins on clay.

However, he has since struggled with knee problems and the last of his season's six titles came in July.

Nadal warned earlier that his record stint at No 2 was under threat from a new generation of players, a prediction borne out by his performances here.

The Spaniard dropped the opening set against eighth-ranked Frenchman Richard Gasquet before coming back strongly, and was out-gunned by Ferrer.

Afterwards Nadal admitted Ferrer's sheer aggression left him struggling to keep up.

"It's very difficult to dictate the rhythm of the game, play aggressive all the time, because he's feeling unbelievable physically," he said.

"I can play like that sometimes, but later I need some calm. I need to rest a little bit in some games."

(China Daily via Agencies November 15, 2007)