Stan Wawrinka believes facing resurgent grass-court king Roger Federer in Wimbledon's quarter-finals is still "one of the biggest challenges in tennis".
The All England Club will host its first all-Swiss quarter-final on Wednesday, after Wawrinka saw off Feliciano Lopez and Federer dispatched Tommy Robredo.
Federer tied up his 12th quarter-final at SW19, swatting the 23rd seed aside 6-1 6-4 6-4, leaving Wawrinka hailing a return to top form for the seven-time champion.
Australian Open winner Wawrinka said Federer's dismal 2013 does not spell the end of the 17-time grand slam winner's era of dominance.
"When you play Roger at Wimbledon, when he's fit and confident and feeling well, it's one of the biggest challenges in tennis," said Wawrinka, after his straight-sets victory over 19th seed Lopez.
"It's like playing Rafa (Nadal) in the French Open.
"Those guys have been playing their best tennis at those two tournaments for many years."
Wawrinka claimed just his second career victory over Swiss compatriot Federer in the final of March's Monte Carlo Masters.
Federer bombed out of Wimbledon in the second round to Sergiy Stakhovsky last summer, failing to reach a grand slam quarter-final for the first time in nine years.
Plagued by back injuries, the stylish grass expert also slipped out of the US Open in a fourth-round defeat to Spaniard Robredo.
Federer avenged that Flushing Meadows loss in fourth-round action at Wimbledon on Tuesday, leaving Wawrinka in no doubt of the challenge ahead.
"When you go on court you need to trust yourself, you need to go for it," said the Lausanne native, who saw off Lopez 7-6 (7/5) 7-6 (9/7) 6-3.
"Last time we played I won, but I lost plenty before that, so it's going to be interesting.
"The win in Monte Carlo will give me a lot of confidence, knowing I can beat him on the big stage.
"But it's going to be a different experience from clay, it's the first time we'll play each other on grass and at Wimbledon.
"In a five-set match, it's going to be tough.
"I know that I'm playing at my best level, so it depends on me a little. I've got to be aggressive on court and if I can do that I have some chance."
He added: "It's sport in general that when a player doesn't play so well he receives many bad comments.
"Roger had back problems last year, so that was the main reason why he was struggling a little bit.
"This year he's feeling great, he's playing better, and that's nice to see - but a tough challenge too.
"What happened to him last year doesn't change the challenge at all, this year it's a different story."
Federer believes Wawrinka's breakthrough grand slam win at the Australian Open leaves his compatriot fearing no one.
"For him the dynamic has changed a lot," said Federer.
"Showing up for the big moments, believing he can come through them now.
"He did lose a lot of close matches against top guys.
"So I'm really happy for him that he's been able to keep it up even though he's had some ups and downs that would be inevitable after a big win like Australia."
Federer admitted his early exits at Wimbledon and the US Open weighed heavily heading into Tuesday's Robredo clash.
Relieved to be back on grand slam par, he said will now chase that open-era record eighth title brimming with confidence.
"The loss against Stakhovsky crossed my mind," he said.
"No doubt the loss against Robredo at the US Open crossed my mind in the last couple of days.
"I had time to think about that, but I must say I kept it in check throughout the match, and also before.
"I was able to impose my game and play well.
"Last year was just frustrating, so I'm happy I'm physically back where I can put myself in contention.
"It's been a tougher last couple of years in terms of slams, but I feel I'm back where I want to be.
"It doesn't matter one bit to me what other people say, last year was tough, but I don't worry about what's going on in the background, I just put my head down and try to win.
"I'm not fighting any confidence issues this year, which is huge in sporting terms."