World No 3 Alexander Zverev flew into a rage as he accused top-two stars Carlos Alcaraz and Jannik Sinner of being 'protected' by the tour after the Spaniard took a contentious medical timeout during their Australian Open semi-final. 

The German star's outburst came during the third set of the marathon five-hour contest, with Zverev going on to serve for the match after he had fallen two sets behind - only for a physically incapacitated Alcaraz to pull off an almighty comeback late on in the fifth. 

The world No 1 had swiped the first two sets of the clash, but began to struggle in the Melbourne heat after a punishing two hours, taking his time to stretch out his groin after losing a point at 4-4. 

Chair umpire Marijana Veljovic opted not to give the 22-year-old a time violation, with Zverev accusing Alcaraz of struggling with cramp and unnecessarily holding up play. 

At the end of his game, Alcaraz summoned the physio to receive treatment - in Zverev's eyes, against the rules of calling for a medical timeout which preclude muscle cramping. 

'He has cramp!' Zverev complained to Grand Slam supervisor Andreas Egli in a mixture of English and German. 'He can't take a medical, he is cramping. What else should it be?

'This is absolute bulls***. This is unbelievable. Cramps? What the f*** is that? You cannot be serious.'

Zverev vented his fury by repeating multiple times that the decision to allow Alcaraz recovery time, via a thigh massage from a physio, was 'unbelievable', 'not possible', and 'bulls***'. 

But in another twist, the 28-year-old stressed that he felt Alcaraz was receiving such leniency because of his position in tennis. 

'You are protecting both of them (Alcaraz and Sinner), this is unbelievable,' Zverev fumed. 'Unbelievable. This is not possible. This is not possible. You cannot be serious.'

Sinner and Alcaraz stand apart at the top of men's tennis, having split the last four Grand Slam titles between them after meeting in the finals. 

The last time a player not named Sinner or Alcaraz won a Grand Slam came nearly three years ago, with Novak Djokovic taking the 2023 US Open. 

Cramping, while officially ruled out as a condition which can prompt a medical timeout, can prove a grey area, with Alcaraz perhaps concerned that he had picked up a thigh injury instead of losing conditioning. 

'From Zverev's point of view, he is viewing it as cramp, and wants to press the pace,' Andy Murray's former coach Miles Maclagan said on TNT Sports. 

'You can understand his argument and a lot of people think if there is a medical timeout then there should be a penalty for it because Zverev's fitness has been unquestionable and that's one of his major strengths which has been somewhat negated by his opponent being able to take a timeout.

'He has worked very hard, not just in this match but across the course of his career to be able to sustain a workrate that is difficult for his opponent. Whether it's cramp or not, it's because of the duress that Zverev was able to put him under.' 

'I think we see a lot with injuries that it's questionable with the physio coming out -  this has been all for Alcaraz's benefit.'

Elsewhere on the tour, strict adherence to the rules has seen players penalised for suffering the physical symptoms of cramp, with former US Open champion Daniil Medvedev initially receiving a 'best efforts' violation after he was rendered immobile mid-game. 

The Russian player was accused of not playing to the best of his abilities during his match against Learner Tien after being bent double in pain on the base line - but later had his violation rescinded upon review. 

Earlier in the third set, Alcaraz told his team that he 'threw up' and questioned whether he should 'take something', due to being unable to take on fluids.  

After the medical timeout and taking slugs of pickle juice to further ease his symptoms, Alcaraz returned to court, but went on to lose the third and fourth sets to push the match to a decider. 

Zverev looked to become the first player to beat Alcaraz in five sets - the Spaniard's specialty of sorts - since the 2022 Australian Open, when he was beaten by former Wimbledon finalist Matteo Berrettini across all five sets. 

The contest ticked towards the five-and-a-half-hour mark as the duo battled on, making it the longest semi-final in Australian Open history.  

But the six-time Grand Slam winner continued his unimpeachable run in the format despite falling a break behind early on, pulling off victory at the very last to win 6-4, 7-6 (7-5), 6-7 (3-7), 6-7 (4-7), 7-5. 

'I always say that you have to believe in yourself, no matter what, no matter your struggles, you've got to still believe in yourself,' Alcaraz said during his on-court interview, appearing almost overwhelmed with exertion and emotion. 

'I was struggling in the middle of the third set. Physically it was one of the most demanding matches I have ever played in my short career. 

'But I have been in this kind of situations before, so I knew what I had to do. I had to put my heart into the match. I think I did it. I put my heart into it until the last ball. I'm extremely proud of myself, the way that I fought, and the way that came back in the last set.' 

Alcaraz was also reminded that, having made his first ever Australian Open final, he will have a chance to compete for a career Grand Slam after previous wins in Paris, London, and New York.  

'Thank you to put so much pressure on me!' He joked. 'I'm just really happy, to have the time to play my first final. 

'It's something I was pursuing a lot, having the chance to fight for the title. I think it's been a great two weeks so far. 

'But one thing I have got to say is that I wouldn't stay here right now, doing this interview, without these guys (the crowd) - it was for me a real pleasure, playing for all of you. 

'The way you pushed me back into the match, it's been crazy. I'm really grateful for the support, not only in this match, but the tournament. Hopefully on Sunday it's going to be a great atmosphere.' 

Alcaraz remained so physically compromised after the titanic clash that his brother Alvaro had to carry his tennis bags off the court. 

He will now recover, and await the results of the day's second semi-final - between Sinner and Djokovic - to learn his opponent on Sunday.