Rooney joined United as one of the world’s best teenage talents in 2003, and left as the club’s record goalscorer in 2017.
The 33-year-old was almost unstoppable at times throughout his Old Trafford stay, but was declining fast by the time Jose Mourinho took over as manager.
Rooney played just one season under Mourinho, winning the Europa League and League Cup, but hardly featuring in either success.
In an interview with Neville for Sky Sports, Rooney says how that was one of the many occasions when his confidence was rocked.
“You obviously had a great England career,” Neville said.
“I always see you as being mentally and physically tough as a player. Are you willing to talk about some of the vulnerabilities you’ve had in the last 15 years?
“Even playing with you I never would have thought you were lacking in confidence, but are there things you can share with the young lads that are here?”
Rooney admitted that he had suffered with a lack of confidence at times, particularly during the closing stages of his Manchester United spell.
“I think there are periods throughout my career where you do lack a bit in confidence, where you doubt yourself at times,” he said. “I think there was a time at Manchester United where I was scoring goals, and then for some reason I couldn’t score.
“You’re down, because I love football, love playing football and after the games I’d go home and watch the games back, to try and see where I’ve gone wrong in certain moments, and I couldn’t work it out. It was so frustrating.
“I couldn’t work out why I wasn’t scoring, why I wasn’t playing as well. Then you end up trying harder, it becomes worse, you feel like you’re just stuck.
“I always remember Sir Alex Ferguson pulling me into his office, and he said: ‘Listen, you’re trying too hard, just keep the game simple. Get the ball, lay it off, get in the box. Your chance will come, you will score and you’ll continue to score.’
“That’s what I did the next game, got the ball, played one or two touch, and I think I scored a hat-trick against Bolton away. I remember sitting there thinking: ‘It can’t be that simple!’ That’s always stuck me when I’ve gone through difficult moments.
“But then, of course, there are times when you doubt yourself as a player, and think: ‘Am I good enough?’ The time Jose Mourinho left me out of the Manchester United team. There are moments when you do doubt yourself, I believe I was good enough to get back in the team, but I never really got that opportunity. I came on for one minute in the Europa League final, I was about to come on against Southampton in the League Cup final, and in those moments it was embarrassing.
“It was getting to a point where I was embarrassed, I thought: ‘I can’t keep doing this,’ as hard as it was to leave Man Utd.
“In the Southampton game, Mourinho came to me and said: ‘I want you to lift the trophy.’ I was like: ‘Well, I didn’t even play in the game.’ He was persistent with it, and I literally lifted it and moved it on!
“I just knew… ‘What was I doing? I need to move on and go somewhere else…’