A campaign image was also shared by all 20 Premier League clubs, to reinforce the importance of remaining indoors as much as possible to reduce the spread of COVID-19.
Here is what Ole and Casey's letter had to say:
'Firstly, on behalf of everyone at Manchester United, our thoughts are with anyone who has been directly affected by this virus and everyone dealing with the impact of it. All our gratitude goes to the healthcare staff working on the frontline of the NHS here in the UK and in hospitals around the world at this particularly difficult time.