Wayne Rooney has dismissed Manchester City's rivalry with Manchester United, saying that the game against Liverpool is his club's real derby.

Asked if the rivalry between the Manchester clubs is now the biggest in English football, Rooney said: "I don't know. They are all big games. Obviously United-Liverpool is a massive game over the years. City have had their success recently but I would probably say that United-Liverpool is still the biggest game."

A goal against Manuel Pellegrini's side on Sunday would make Rooney the all-time leading scorer in Mancunian derbies, City's Francis Lee and Joe Hayes being level with Rooney on 10 strikes in derbies, and David Moyes believes this can be a further driving force for him as he aims to prove his doubters wrong. "The thing is to keep his form. If he keeps playing the way he has the goals will come," the United manager said. "He'll go on and keep scoring goals. I think to keep playing with the level of intensity he has got is important."

Moyes explained: "He's got a bit of that old toughness back. I wouldn't say he has lost that but I think folk might say: 'I don't see it quite as much about him.' Physically he is able to do it. And mentally he's probably got a bit of a cause in his head: that he's going to show everybody. And he can do that. He's got that about him." Following Rooney's two goals in Tuesday evening's 4-2 win over Bayer Leverkusen in the Champions League, Sir Alex Ferguson praised the striker, saying he was back to his best. The rift between the two had been seen as a key factor in the player's desire to leave.

Moyes believes Ferguson's words will give Rooney a boost. "I think when you get a compliment from Sir Alex you take it for what it is," he said. "I don't say he doesn't give them out freely but I'm sure Wayne will have heard that. But we've got to remember it was Wayne who has put himself in the position, Wayne who has done the hard work – so it's not to do with David Moyes or Sir Alex Ferguson.

"It's Wayne Rooney who's got himself in a real good physical condition, as I talked about in pre-season. Mentally we needed to see a Wayne Rooney who was aggressive and all-action, which he was capable of being. He was different: he could score, he could fight, he could work for the team. He had all those attributes in his game and I think recently everyone's begin to see all those attributes come back."

After the win over Bayer, Rooney said that he and Moyes could achieve great things together. Did Moyes think the comments meant Rooney was now content to remain in the long term? "I didn't think there was a line to draw anything under with me and Wayne. The club sort of made that known and now Wayne realises that this is the situation [that he should stay]. The thing about Wayne is that it's a big year for him – all the records that he could try and get towards. He's got a big year towards the World Cup. I think he would say that last year, by his standards, wasn't his best season. So you want to improve on that and he's set out his own stall to show he's going to improve on that."

Rooney's contract expires in two years with the club expected to open talks with him sometime this season. "We just do it step by step," said Moyes. "Just to see him score another two goals at the weekend [against City] will be the next step, just to keep his form going. I think he's played well and we want him to maintain to it. If anything I am asking him to step up again and keep getting better.

"Having players like Wayne Rooney at your club gives you the chance of making a difference maybe when the games are tight. You want special players and if Wayne keeps up the levels he's shown in the last couple of games then he is certainly going the right direction to show he is one of these top players. Wayne's attitude is that he's a big game player. People come to see people like him make the difference and hopefully he can do that."