Andy Roddick accepts he can't break Lleyton Hewitt mentally and is gearing for a mighty struggle despite his recent edge over his Wimbledon quarterfinal opponent.

The pair renew an eight-year history today with Hewitt leading their career encounters 6-5, but the American sixth seed has won their past four meetings, including a straight-sets victory on grass at Queen's last month.

Hewitt, however, points out big-serving Roddick's 7-6 (7-2) 7-6 (7-4) win in the Wimbledon warm-up came down to "only one or two points" and the Australian didn't face a single break point.

His chances of advancing to a likely semifinal clash with third seed Andy Murray most likely will rest on his reaction to just a handful of chances against such a strong-serving game.

"You know you're going to get aced out there," Hewitt said. "You know he's going to come up with big shots.

"You've got to weather the storm and take those small chances when you get the opportunity."

Both players concede they have met so many times one is unlikely to surprise the other.

"It's a fight, everything is a fight, Lleyton's not going to give you anything," Roddick said. "A lot of guys you can get on top of, you can get on top of their game, you can look for holes in it.

"Lleyton doesn't really have a lot of holes. You're definitely not going to get on top of him mentally. He's as sound there as anybody."

The question mark for Hewitt is a left thigh injury which needed treatment in his trademark fight-back to overcome Czech No. 23 seed Radek Stepanek 4-6 2-6 6-1 6-2 6-2 on Monday. But the 2002 champion was confident his physiotherapist Ivan Gutierrez would have him close to full fitness.

"He knows my body as well as anyone," Hewitt said.

"I'm sure I'll be very close to 100 per cent by Wednesday."

The comeback win over Stepanek was the first time 56th-ranked Hewitt had dropped a set all tournament but his recovery secured a place in his first grand slam quarterfinal since 2006.

Roddick has had a slightly tougher path to the last eight.

After being pushed to four sets in his first three matches, he eased past another Czech, 20th seed Tomas Berdych, 7-6 (7-4) 6-4 6-3.

Heartened by Hewitt's form, former Davis Cup captain John Newcombe dismisses Roddick's recent success against the former world No. 1. "He (Hewitt) had the wood on Andy 6-1 when he was playing his best tennis," Newcombe said.

"He lost the last four when he was a bit off.

"Injury-free, he will beat Andy."

Hewitt paid tribute to his vocal supporters, who have become a focal point at Wimbledon this year and whose spirits were not dampened after being spoken to by stewards.

Hewitt thanked the group, mainly ex-pat Australians living in London and members of the travelling Fanatics supporters' group, by handing them his towel and a clutch of wristbands after the match.

And while he admitted to drawing energy from them, Hewitt did not believe their good-natured chanting distracted his opponents.