Rio Ferdinand says he has missed "the chemical that comes out of you" in professional sport as he launches a new career as a boxer.
The 38-year-old announced on Tuesday that he is to try his hand in the ring with the view to challenging for a belt over the next 12 months, just two years after retiring from football.
Although the former Manchester United defender insists he does not expect to progress as far as global title bouts, he is eager to experience the thrill of competition and to test himself "as a human being".
"A lot of people sit and watch huge fights, plus other sporting events and say 'I can do that' or 'they've messed it up'," he told Standard Sport.
"There are a lot of armchair fans wanting to pass judgement. Well, I'm going to walk the walk and actually do it.
"I'm into keeping fit and one of the big things I have missed since retiring from football in 2015 is the competition, whether it be as a team or as an individual going one-on-one against a striker.
-- DefenderToContender (@Betfair) September 19, 2017
"I just miss that chemical that comes out of you. I have not been able to replace it. This is a great way to get that back.
"I'm doing this for many reasons. I'm doing this to test myself as a man, as a human being.
"Can I change sports? Can I be a respectable performer in other sports? Can my body get through it?
"Can I mentally get up early at 5-6am in the morning when it is dark and cold to go on long, dirty runs? Then get back, take my kids to school, go to the gym and eat properly all of the time.
"This is a test of my mind and body, that's the way I'm looking at it. I'm not looking at it to become the world champion, I'm not stupid."