Wayne Rooney was told he had "gone a bit soft" by David Moyes as the Scot revealed how last summer he managed to persuade the disillusioned striker his future remained at Manchester United.

Rooney's renewed commitment to the club, putting pen-to-paper on an £85m, 5½-year deal, is a major coup for the United manager. His relationship with the striker, as the man who handed the 16-year-old prodigy his Premier League debut at Everton, permitted a searing honesty with England's finest footballer.

At two meetings with Rooney, before officially taking charge of United on 1 July, Moyes hardly minced his words. The Liverpudlian had lost his way under Sir Alex Ferguson and was determined to leave in the summer transfer window for Chelsea.

Moyes said: "I remember when he came to see me. He came up to my house. I said to him: 'If you ask me what's missing – I think you've gone a bit soft.' I thought he hadn't been the hard-working, aggressive player he was. But now in games people are saying: 'Look at the effort he's putting in.' It's his work-rate, not just for himself but for the team. He's become an all-round team player who is also a technically gifted footballer.

"I said to Wayne that I wanted him to stay. Before I'd actually come in here, I'd met Wayne privately a couple of times, to talk about his situation, to try to understand. So when I got in [on 1 July] I knew where Wayne was. The most important thing for Wayne was to show everyone what he really was and I think deep down he knows he didn't play as well as he could have done at times. I needed to try to get him back to that level. But in the end I just said to him: 'Wayne, go and get on with it.' His training was first-class, he came back in great shape, you could really see the hunger back in his eyes again."

Moyes fell out with Rooney previously due to comments the player made after departing Everton in 2004. After Moyes won a 2008 court case for libel and later received an apology from Rooney, the striker further underlined his respect by accepting that he may, indeed, have gone soft.

"I said: 'I've watched you, I've not been your manager, I just think you had better get back to the old aggressive Wayne Rooney,'" Moyes said. "And I think he thought: 'Yes, maybe that.' But what he had to get to was a level of fitness where he was able to produce again. He was brilliant in the way he trained and wasn't a minute's problem."

Rooney has 208 goals for United in 430 appearances, so the new deal means he should comfortably surpass Bobby Charlton's club record 247 in 754 games.

This formed part of his decision to stay. "I think that was behind it," Moyes said. "To be a legend at Manchester United it is something where you are associated with this club for the rest of your life. The one thing I've noticed since I've been here is no one wants to leave Manchester United very quickly.

"For Wayne, he's recognised [how] people like Bobby Charlton, George Best – the way those big stars are seen here. Wayne's next thing is that we have to keep challenging him to get those goals, make those big targets."

Moyes believes Rooney can improve. "All we've done is say to Wayne you need to get back to where we think you were," said the Scot. "There is more to come as an all-round team player, leader, person."

While Moyes would not formally confirm Rooney will replace Nemanja Vidic as captain, there will be a major surprise if he is not wearing the armband during United's pre-season tour of the US. "Yes, it's possible but I wouldn't want to say until the summer time," the manager said.

It is some transformation. A year ago Rooney was dropped by Ferguson for the Champions League meeting with Real Madrid, the club's biggest match of the season. Now, he is the man Moyes's new United will be built around.

In what is proving a trying inaugural season, Moyes has rarely looked as happy as he did , talking about Rooney's decision. "I'm thrilled, delighted, really pleased. He's a wonderful player," said the manager. "When he came into the team I felt as though he nearly had to reinvent himself again. Go back to being the old Wayne Rooney, aggressive, fighting for everything that's there, but with the level of technical ability of a top player which he's got. He's done that. He's back, he's showing leadership qualities. He's shown exactly what it is to play for Manchester United."