Now, the Northern Irishman has explained why he's such a bundle of energy in the technical area - he wishes he was still playing.
As he riles up his Villans for Sunday's Second City derby with Birmingham, the 56-year-old has revealed that he urges his players to enjoy every second of their playing days.
"Playing is the ultimate. Managing is second best", the former Leicester and Celtic gaffer said.
"It is difficult for people (to understand), like the players today, because you don't think you are going to get older.
"You stay 25 for the rest of your life. You think it will never end, I did that myself. Then one day it is over.
"So, don't let anyone tell you that this managing is great fun. It is not in the same league as playing."
He continued, "I always want them to really believe that."
"I don't think that every single minute of the day you should be running around thanking and praising the heavens, but you should realise that it is a really privileged job that you get paid for doing something you love and paid for keeping yourself fit.
"At the end of the day it is a privileged life. If you happen to be really great at it, it is the ultimate, isn't it?
"It genuinely is the ultimate. And if you stay clear of serious injury and your health is okay, my what a time!"
O'Neill insists that the big difference between playing and managing is that players only have to look out for number one.
"Generally speaking, whatever you say about the playing side, you are looking after yourself. But the manager has to see it from a different perspective, a more collective perspective."