Lleyton Hewitt overcame a brief injury scare on Saturday, two days before his opening match at Wimbledon.

Hewitt lost his footing during practice with the French Open runner-up Robin Soderling and remained on all fours at the baseline for some time, even prompting a concerned wince from his hitting partner.

When the Australian rose to his feet, he was clearly in pain, clutching his left hip.

But he continued to train, apparently unhindered, for about another 30 minutes.

Hewitt, the 2002 Wimbledon champion, is working his way back up the rankings after undergoing surgery on the same hip, which sidelined him for four months at the end of last year.

In February, he dropped out of the top 100 for the first time in a decade, and is now ranked 56th.

Hewitt and coach Tony Roche declined to speak after the training session.

The 28-year-old is preparing for a first-round clash with American Robby Ginepri on Monday.

Hewitt has beaten the American five times in as many meetings.

Meanwhile, the top men's seeds expressed disappointment at the withdrawal of defending champion Rafael Nadal due to knee problems.

Five-time winner Roger Federer, who lost his crown to Nadal in an epic final last year, said he was saddened by the news.

"That's disappointing for me, of course, because I'd love to play him," Federer told reporters.

"He's my main rival. We've had some wonderful matches over the years, and especially the one here last year was the one that obviously stands out.

"It's unfortunate. I'm sad for him, because it must have been a very difficult decision to make."

No.3 seed and British hope Andy Murray agreed.

"I'm sure everyone would have liked to have seen him here," Murray said.

"He's my favourite player to watch, so I'm sure the fans that wanted to come to see him will all be disappointed, but he's got to do what's best for him."

Hewitt was on track for a second-round clash with the world No.1 but now faces a likely meeting with fifth seed Juan Martin del Potro, who took Nadal's place in the draw.

The Argentine plays Arnaud Clement of France in the first round.

At the AEGON International in Eastbourne, a classic warm-up for Wimbledon, Australian duo Samantha Stosur and Rennae Stubbs lost their doubles final against Akgul Amanmuradova of Uzbekistan and Japan's Ai Sugiyama 6-4 6-3.AAP