London - Hobbling Juan Martin del Potro and Polish trailblazer Jerzy Janowicz hope to derail the Wimbledon title dreams of Novak Djokovic and Andy Murray, the world's two best players, in Friday's semi-finals.
Del Potro, the 2009 US Open champion, just about survived his quarter-final against David Ferrer when he strained his already heavily-bandaged left knee in a sickening Centre Court tumble.
The giant Argentine now tackles world number one and Australian Open champion Djokovic.
Janowicz, the first Polish man in the last-four of a major, takes on US Open and Olympic champion Murray who is bidding to be the first British man in 77 years to win Wimbledon.
Djokovic has an 8-3 winning record over Del Potro but the Argentine won their only other previous meeting on grass in the 2012 Olympics bronze medal play-off which took place at Wimbledon.
Del Potro also won the pair's last meeting in March, on hard court in the Indian Wells semi-finals.
But Djokovic, having escaped the shock exits suffered by the likes of Roger Federer and Rafael Nadal at this year's Wimbledon, believes that he can still play better.
"It's the mindset I always try to have, because that's something that keeps me going every single day on the practice courts, day in, day out, trying to give my best and trying to always inspire myself to play better tennis," he said.
"I know I have a quite complete game, but I still feel there is room for improvement."
The Serb, the 2011 Wimbledon champion, will be playing in his 13th successive Grand Slam semi-final, 10 behind the record held by Federer.
At Wimbledon this year, he is chasing a seventh major.
Top seed Djokovic won't be lulled into a false sense of security by the injury-cursed Del Potro's latest problems.
The 24-year-old eighth seed is used to tackling physical problems.
In 2010, he played just three tournaments and saw his ranking slip to 257 in the world after undergoing wrist surgery.
"He struggled with injuries in last few years, but every time he comes back he comes back very strong because he just has this talent and qualities as a player," said Djokovic.
Del Potro's 2009 US Open win was the only time in the last 33 Grand Slams that the champion wasn't called either Federer, Nadal, Djokovic or Murray.
Like Djokovic, Del Potro has reached the last-four - his first semi-final at Wimbledon - without dropping a set.
"I will need to be 110 percent against Novak. He's the number one. He's a former champion. It's going to be a more difficult match for me," Del Potro said.
Second-seeded Murray, the runner-up to Federer in 2012, will be playing in his fifth consecutive Wimbledon semi-final, but he had to come from two sets to love down to beat Fernando Verdasco in the quarter-finals.
It will be his 13th major semi-final, equalling the national record set by Fred Perry, the last British man to win the title in 1936.
"It will be a very tough match. Janowicz has a big serve. He's a big guy with a lot of power," Murray said of his Polish opponent who has fired a tournament-leading 94 aces at Wimbledon this year.
They have a 1-1 record but Murray lost their last meeting at the Paris Masters in 2012 when Janowicz came through qualifying to reach the final.
"He also has pretty good touch. He likes to hit drop-shots. He doesn't just whack every single shot as hard as he can," the Scot said.
Janowicz, the 24th seed, is this year's rags-to-riches Wimbledon story.
When he once played the US Open, New Yorkers coughed up to buy him tennis shoes while, two years ago, when he was ranked at a lowly 221 in the world, he didn't have the cash to buy a ticket to the Australian Open.
"I have had some troubles during my career. You practice and work for these kind of moments," said Janowicz, who broke down in floods of tears on Wednesday when he defeated compatriot Lukasz Kubot.