Michael Carrick has said he suffered with depression following Manchester United's Champions League final defeat to Barcelona in 2009.
The 37-year-old former United midfielder gave the ball away in the build-up to Samuel Eto'o's opener as the Catalan club denied Sir Alex Ferguson's side back-to-back victories in Europe's premier club competition.
Carrick described the defeat as the "biggest low" of his career and said he kept the issue to himself rather than opening up to his team-mates.
He told the Times: "It was the biggest low of my career by quite some way and I don't really know why. I thought I'd let myself down in the biggest game of my career. I had won the Champions League the year before but that was totally irrelevant.
"It felt like I was depressed. I was really down. I imagine that is what depression is. I describe it as depression because it wasn't a one-off thing.
"I felt bad or terrible after some games but then you get over it in the next couple of days - but that one I just couldn't shrug off. It was a strange feeling.
"I beat myself up over that goal. I kept asking myself 'Why did I do that?' and then it snowballed from there. It was a tough year after that. It lingered for a long time.
"I kept it to myself most of the time. Even my family didn't know the full extent of it. It's not something that's really spoken about in football. I have not spoken about it before.
"For the lads that I have played with that are reading this, this will be the first time that they know."
Carrick said footballers are expected to be able to play well week after week but insisted that is not always easy.
"As a footballer you are expected to be that machine that just churns out results after results, performance after performance," he added.
"You are paid well and you play for a big club so why can't you be good every week? It's just not like that. It's not easy to do that and it's easy to forget that. There could be all sorts going on that you don't know about."
Former England man Carrick also revealed that he wanted to come home from the 2010 World Cup in South Africa over a year after the Champions League final as his struggles continued.
He said: "In 2010, that was the worst time. It was my dream to be at a World Cup but the truth is that I didn't want to be there. I wanted to be at home.
"I was telling (his wife) Lisa 'I've had enough. I want to come home'. I wouldn't have done but that's how I felt."