Rafael Nadal is facing a race against time to be fit for Friday's mouthwatering Wimbledon semifinal against Nick Kyrgios but can either man stop Novak Djokovic in his relentless push for a fourth straight crown?
A meeting between 22-time Grand Slam champion Nadal and the mercurial Australian has been on the cards since Kyrgios defeated Stefanos Tsitsipas in an ill-tempered third-round meeting.
Kyrgios cruised through his last-eight match against unseeded Chilean Cristian Garin on Wednesday in straight sets to reach his first Grand Slam semifinal.
But it was a different story for Nadal, who had to battle an abdominal injury in a grueling five-set win against 11th-seeded American Taylor Fritz.
The second seed, visibly in pain, looked unlikely to finish the match when he was forced to take a medical time-out in the second set.
But he returned to the court and twice recovered from a set down to win in 4 hours and 21 minutes.
The extra time on court for Nadal – two hours longer than Kyrgios – is a factor in itself but the Spaniard's injury raises the prospect that he may not even be fit enough to play.
Nadal, the 2008 and 2010 champion, said he was unsure over his ongoing participation in the tournament as he targets the third leg of a rare calendar Grand Slam.
"I can't give you a clear answer because if I gave you a clear answer and tomorrow another thing happens, I will be a liar," the 36-year-old said after his quarterfinal win.
If the two do meet on Centre Court, it would be the standout tie of the tournament so far in a year when many of the top seeds have fallen by the wayside early.
Kyrgios's tournament has been defined by breathtaking shot-making but also his familiar rants on court – including a demand that Tsitsipas be thrown out of the championships for hitting a ball into the crowd.
The 40th-ranked player has been fined a total of $14,000 and he now has the added distraction of a looming court appearance in Australia, related to an allegation of assault.
Nadal has six wins against Kyrgios in nine meetings between the pair.
The Australian famously beat Nadal – then-world No. 1 – on his way to the Wimbledon quarter-finals on his debut in 2014 but the Spaniard took his revenge in 2019.
Kyrgios, 27, said he believed the match against Nadal would be the "most-watched of all time."
"We've had some absolute battles on that Centre Court," he said. "He's won one against me and I've won one against him.
"Obviously, we know, two completely different personalities. I feel like we respect the hell out of each other, though. I feel like that would be a mouth-watering kind of encounter for everyone around the world."
Djokovic had to come back from two sets down against Italian 10th seed Jannik Sinner in his quarterfinals on Tuesday.
But the 35-year-old finished the match looking fresh, even pulling off an outrageous winner while doing the splits.
The Serbian top seed is on a 26-match winning streak at Wimbledon as he seeks to draw level with Pete Sampras on seven titles at the All England Club – just one behind Roger Federer's men's record.
British ninth seed Cameron Norrie has vowed to "take it" to Djokovic and will hope to ride a wave of home support but he has a tough task on his hands to unseat the champion.
Djokovic, who beat the 26-year-old in their only previous meeting, is braced for a partisan crowd.
"For him, not much to lose," he said. "Every victory from now onwards is a big deal for him.
"I know that. But, you know, I practiced a few times. I know his game well. He's been around. Of course, I will do my homework and get ready."