What bubble system?
I don't believe players are home-bound once they've left training, although I would expect most players will be sensible enough not to "do a Grealish". Despite that, some will have partners out at work, kids at school and will meet up with other friends and family. Some will become infected and when they do, it will probably only be the luck of speed of detection that prevents it spreading throughout a squad.
not my idea to call it a "bubble" and I agree its a very weak kind of defense with so many other variables in life not just football training and match's
a very limited bubble surrounding the training ground and stadium can only do so much and as is now showing wont stop the spread into the game , best we can hope for is it stays on the outer edges with the odd positive and not whole squads which looks more likely to happen from recent tests
hate to be negative about it but going into winter makes the spread more likely than ever