London - Roger Federer and Andy Murray will attempt to make the most of Novak Djokovic's shock Wimbledon exit and book their places in the quarter-finals on Monday.
Federer, the seven-time champion, had been seeded to face world number one Djokovic in the semi-finals having lost the 2014 and 2015 championship matches to the Serb at the All England Club.
Now, the 34-year-old is comfortably the favourite to reach his 11th final from the top half of the draw.
But first he must get past Steve Johnson, the world number 29 from the United States who has never before made the last 16 at a Grand Slam event.
Federer said it was unreasonable to expect Djokovic, who had held all four Slam titles, to keep on winning.
"I always said it: the first week is tough. Margins are small. I know we get carried away, we think it's impossible to beat him, all these things. Clearly he's beatable. It's not impossible," said the Swiss.
"He cannot win straight 200 matches in tennis. You're going to have your losses."
Johnson won on grass at Nottingham and was a quarter-finalist at Queen's in the Wimbledon build-up.
But he has never played Federer.
"I think it's going to be exciting. I have never played on Centre," said the 26-year-old.
"It's going to be a great experience. I'm going to go out there thinking I'm going to be the winner. I have no fear out there."
MURRAY FACING PAL KYRGIOS
Second seed Murray, the 2013 champion, has breezed into the fourth round without dropping a set.
But he faces a tough task on Monday against Australian 15th seed Nick Kyrgios.
Murray has a 4-0 career lead over the Australian with three of those meetings having come in the four majors.
"Our relationship's pretty good," said 21-year-old Kyrgios, who defeated Rafael Nadal at Wimbledon in 2014 on his way to the quarter-finals.
"We joke a lot. When he's in the locker room, it's just instant banter."
Sam Querrey, the American 28th seed who knocked out Djokovic in the third round, is in the last 16 for the first time in six years.
He faces French grass court specialist Nicolas Mahut, who holds a 2-0 lead over the American including a win on grass at 's-Hertogenbosch last month.
Canadian sixth seed Milos Raonic, a semi-finalist in 2014, meets Belgium's David Goffin, the 11th seed.
Marin Cilic tackles Japan's fifth seed Kei Nishikori in a repeat of the US Open final of 2014 which Cilic won.
Richard Gasquet and Jo-Wilfried Tsonga meet in an all-French duel. Both men are two-time semi-finalists at the All England Club.
They are locked at 4-4 in career meetings but have not played each other for more than three years.
In an all-Czech match-up, world number 64 Jiri Vesely, who beat Djokovic in Monte Carlo this year, takes on 10th seed and 2010 runner-up Tomas Berdych.
It will be Vesely's first appearance in a Slam fourth round.
French 32nd seed Lucas Pouille is also in unchartered waters when he faces 2011 quarter-finalist Bernard Tomic.
Bookmakers have Murray as the favourite for the title at evens, ahead of Federer, Raonic and then Kyrgios.