London: Roger Federer is braced for the toughest examination yet of his Wimbledon title credentials after reaching the quarter-finals without a serious test.
The seven-time champion has lost just one set in four rounds, but that was a mere blip on a tie-break during an otherwise controlled victory over Australian Sam Groth, and the 33-year-old has yet to drop his serve.
The latter factor shows Federer is sending down the ball as well as ever, however he expects Frenchman Gilles Simon to return better than anyone he has tackled, and accepts that may mean his serve takes some punishment.
"Gilles Simon is one of the best return players we have in the game. I would think I'll be tested a lot," Federer said. "That streak is maybe coming to an end, in my opinion."
Federer joked that his opponents until now have been "returning terrible".
In their previous grand slam matches at the 2011 Australian Open and 2013 French Open, Federer has been taken to five sets both times by Simon, a 30-year-old born in Nice but resident in his opponent's native Switzerland.
The Frenchman is wary of Federer's prowess at Wimbledon though.
"Facing him on grass, I don't know," Simon said. "We have never played on grass. I think he's playing really well right now.
"I will just go out there and try to play what I've been playing from the beginning of the tournament and from the beginning of the grass-court season.
"We often had some close matches with Roger. He destroyed me once, so I'm ready and know it can be sometimes difficult to face him, but one more time I just feel good and I just want to play it."
Their match is first on Court One, ahead of another clash of players from Switzerland and France as Stan Wawrinka takes on Richard Gasquet.
Home favourite Andy Murray opens up Centre Court proceedings against surprise quarter-finalist Vasek Pospisil, with Novak Djokovic then playing the US Open champion Marin Cilic and looking to augment a 12-0 career head-to-head record against the Croatian.
Cilic takes inspiration from how he bustled all the way to grand slam glory in New York last September, and the 26-year-old is not running scared of the defending men's champion.
"I'm going to have to be more aggressive to play more risky tennis," said Cilic, whose coach is the 2001 Wimbledon champion Goran Ivanisevic.
"Of course that leaves less margins for error, but that's the way I was playing last year.
"I think this would be the best opportunity for me to try to play full on."