A bullish mood is spreading among his rivals that dominating world number one Roger Federer is beatable coming into the showpiece rounds of the Australian Open.
The Swiss top seed, the winner of 12 Grand Slam titles, second only to Pete Sampras' 14, has ruled men's tennis for four years and has been a constant in the last 10 major finals.
But Serbian Janko Tipsarevic started the whispers when he expectedly dragged Federer into a five-set dogfight in the third round, with the three-time Australian Open champion having to pull out all stops to survive.
Federer got back on track with a straight sets demolition of Czech Tomas Berdych and now he has James Blake in the quarters and a potential showdown with ambitious young Novak Djokovic in the semis.
The Swiss supremo is taking an unbeaten 18-match tournament run into Wednesday's match with the American 12th seed, who has yet to beat Federer in their seven meetings.
Blake has taken just one set off Federer -- in the quarter-finals of the 2006 US Open -- and reveres the unflappable Swiss, but is encouraged by what he saw in the four-and-a-half hour scrap Federer had with Tipsarevic.
"It's just a reminder that everyone's human. You can have a bad day. It just shows that there are enough guys out here who can play on their best day and give him trouble. It hopefully can raise my spirits to know that I can do the same," Blake said.
But he knows what he will confront across the net on Rod Laver Arena against the man who is fast closing in on becoming the all-time greatest, if he is not already.
"He tends to put constant pressure on you by making tons of returns. He's going to put so many in the court that you don't get free points," Blake said.
"I know it's going to be difficult, but if I can make a lot of first serves, I hope that will give me some confidence and be able to go after my shots."
Federer has seen it all and knows he will again be under pressure to win.
"I know his game suits my game. I've had some great matches against him where I always play my very best. I'm excited to play against him. He's one of the nicest guys on tour, very respected on tour, very sportsmanlike," he said.
Should Federer get through he will more than likely come up against fast-rising Djokovic, allowing that the 20-year-old Serb overcomes Spanish fifth seed David Ferrer in Wednesday's other quarter-final.
There is much anticipation that Djokovic, who hasn't dropped a set, is edging closer to a Grand Slam title after squandering seven set points in the first two sets of a straight sets loss to Federer in last year's US Open final.
"So far I've been performing very good tennis. I have a very difficult opponent in David Ferrer, the guy I lost to in the Masters Cup," Djokovic said.
"He doesn't have anything to lose here. He's been playing some amazing tennis. It's going to be a tough match for me, so we'll see what happens."
Ferrer, who is looking to wear down Djokovic from the back court, leads 3-2 in their matches, with the Serb beating him in the semi-finals of the 2007 US Open.
But Djokovic, who was impressive in dispatching former finalist Lleyton Hewitt in the fourth round, is eyeing another possible crack at Federer and can't help talking about it.
"The players start to feel that he's beatable. Of course, nobody's unbeatable," Djokovic said.
"But he was very dominant, especially on the faster surfaces and he's been the number one player for a while.
"The players started playing in a different way against him, with more belief that they can win. So it's a good thing for all of us."