Manchester United star Marcus Rashford usually looks admirably serene and poised despite his tender age. Even after the 23-year-old made history last week by netting the fastest-ever Champions League hat-trick as a substitute against RB Leipzig, he still appeared calm and cool-headed during his post-game interview. 

But on Sunday, Rashford lost his composure after he was told that Sir Bobby Charlton, who was widely considered to be Manchester United's greatest ever player and a key member of England's 1966 World Cup-winning side, had been diagnosed with dementia.  

"Sir Bobby, you are my hero and I am devastated that you are having to go through this," an emotional Rashford penned on Instagram after posting a picture of him shaking hands with Charlton during an England training session. 

"I filmed alongside this man as a child and was in awe. I still am when I see you. This man, from day 1, was everything I wanted to be. Kind, professional, caring, talented," he added.

Rashford's worry is understandable. Just two days ago, the 83-year-old's former United teammate Nobby Stiles died after a prolonged period with dementia and prostate cancer. And in July, Charlton's elder brother, Jack, also died following a battle with dementia and lymphoma. 

Manchester United, where Sir Bobby won three league titles, a European Cup and a FA Cup during a glittering 17 years, are equally concerned. "Everyone at Manchester United is saddened that this terrible disease has afflicted Sir Bobby Charlton and we continue to offer our love and support to Sir Bobby and his family," read a statement. 

Charlton is the fifth member of England's World Cup-winning squad to be diagnosed with dementia, after Stiles, Jack, Martin Peters and Ray Wilson. This tragic trend was highlighted by former England striker Gary Lineker. 

"Yet another hero of our 1966 World Cup-winning team has been diagnosed with dementia. Perhaps the greatest of them all, Sir Bobby. This is both very sad and deeply concerning," he said on Twitter.

Research by Glasgow University in 2019 found that professional footballers are three and a half times more likely to die of dementia after retirement than people of the same age range in the general population. 

It compiled the medical records of 7,676 men who played professionally between 1900 and 1976, with their data matched against more than 23,000 individuals from the general population. 

The study was commissioned by the Football Association (FA) and the Professional Footballers' Association (PFA) and was led by consultant neuropathologist Dr Willie Stewart, who found that footballers had higher risk of death from neurodegenerative disease. 

"This is the largest study to date looking in this detail at the incidence of neurodegenerative disease in any sport, not just professional footballers. Our data show that while former footballers had higher dementia rates, they had lower rates of death due to other major diseases," he was quoted as saying by the BBC.  

"As such, while every effort must be made to identify the factors contributing to the increased risk of neurodegenerative disease to allow this risk to be reduced, there are also wider potential health benefits of playing football to be considered," he added.

Charlton's tragic diagnosis could inject some urgency into the attempts to initiate more research on the prevalent dementia problem in world football as there are many questions that still need to be answered. 

"The whole game must recognize this is only the start of our understanding," said FA Chairman Greg Clarke. "It is important the global football family now unites to find the answers and provide a greater understanding of this complex issue." 

The stance was supported by PFA Chief Executive Gordon Taylor, who stressed that research must "continue to answer more specific questions about what needs to be done to identify and reduce risk factors." 

Until that happens, the only thing Sir Bobby's worldwide admirers could do is to pray and wish him well. 

"Stay strong, we love you," said Rashford in his latest post before signing out.