Jannik Sinner crashed out of the ongoing French Open, losing to Juan Manuel Cerundolo 6-3, 6-2, 5-7, 1-6, 1-6. Especially with Carlos Alcaraz withdrawing, Sinner was the favourite to clinch the title at Roland Garros and complete a career Grand Slam. He has won the Australian Open (2024, 2025), US Open (2024) and Wimbledon (2025). But has never won the French Open.Jannik Sinner suffered from fatigue and cramps in his second round exit. (AFP)Sinner was on the brink of victory in his second-round match against the Argentine, but heat-related fatigue led to cramps.Also Read: Novak Djokovic loses to 19-year-old Joao Fonseca, eliminated from French Open in 5-hour five-set thrillerHe was holding a two-set lead and commanding a 5-1 advantage in the third before collapsing and sliding to a shocking defeat. 1997 US Open finalist Greg Rusedski feels that Sinner could be suffering from a virus, which also contributed to his semifinal defeat to Novak Djokovic at the Australian Open this year."It’s basically heat exhaustion, or maybe he had something with the virus he had in Australia," he said, while speaking on his podcast.Pointing out that it wasn't a mental issue as the Italian was 5-1 up in the third set, he said, "Everybody’s saying, Sinner’s got a weakness and it’s mental. That’s nonsense. He’s not going to choke when he’s two sets to love up and 5-1 against a guy who is beating him easily."‘I heard he had a virus in Australia’Rusedski claimed he heard Sinner had a virus in Melbourne that held him back. "I heard he had a virus in Australia that was holding him back and these viruses can linger. When you are winning matches as easily as he has been, you can cruise through matches, but the heat got him in Paris. That’s the only explanation that makes sense to me," he said."Sometimes viruses take a long time to get out of your system. Look at Emma Raducanu over the last few months."Jannik also said he felt sick on the morning of the match."So the only people who actually know what the truth of the matter is Jannik Sinner and his team. And he’s got a fantastic team. They will be looking at everything. The agent will be looking at everything. They will find a solution to this problem."But they also don’t want to tell us what the problem is exactly, which is also good coaching because it makes us talk, what is it? What’s happening here? What’s happening there? Because you don’t want to give any advantage to your opponents," he added.