Chelsea boss Graham Potter is upset for his former Brighton midfielder Enock Mwepu.
The Zambian has been forced into retirement due to a heart condition.
Potter said at his Champions League media conference: "Really terrible, but thankfully, it isn't as terrible as it maybe could've been because I think he has been as lucky as he can be in the sense that he is alive and well.
"That is something we're really thankful for. But at 24 years old, to now be able to play football puts everything in perspective.
"I tried calling him today – I sent him a message – he is a fantastic person, and whatever he does, he will succeed in his life. But it's a shame we won't see him on the pitch."
