Wayne Rooney may not be quite ready to declare that he has found renewed happiness at Manchester United, but he definitely looks content.

Leaner, sharper and, above all, liberated to play a much more attacking role by Marouane Fellaini's newly installed presence in central midfield, Rooney seems in perfect shape for Sunday's Manchester derby at the Etihad Stadium.

"It's a massive game," Rooney said. "Two title contenders. It's not going to define the season but it's a big game, a derby. We'll be going there to win. I've scored a few goals against City."

He warmed up for his first opportunity to upset Manuel Pellegrini with a couple in Tuesday's 4-2 Champions League win over Bayer Leverkusen at Old Trafford. It was an evening when David Moyes seemed to cast off his cloak of pragmatism and embrace an attacking philosophy which, in attacking moments, sometimes saw United morph into 4-2-4 formation.

With Fellaini holding midfield alongside Michael Carrick, Rooney was not required to drop deep and do so much defensive work as in recent months, with the benefits clearly, and quickly, apparent.

Indeed Moyes is keen for Rooney and Robin van Persie to have a more traditional partnership than they experienced last season, when the England forward frequently spent considerable time containing opponents while effectively deployed as a fifth, sometimes wide, midfielder. United's manager wants both his key strikers deployed high up the pitch and taking it in turns to drop deeper and help support the midfield when required.

"The times when Robin and I played together last season we did well," Rooney said. "So hopefully we can play more together this season. We've done the work [in training] together. The manager has made it clear he wants one up and one behind. Whatever way round it is doesn't matter as long as one is always filling in behind and helping out the midfield."

Rooney is adamant his relationship with Van Persie lacks jealousy or hierarchy. "Robin and me dovetail well and try and help each other score goals," he said. "I've seen things said over the summer but me and Robin are friends off the pitch. There's no problem between us at all. We're great friends and want to help each other be successful."

His rapport with Moyes also appears surprisingly healthy given the furore surrounding Rooney's desire to leave Old Trafford and leap into José Mourinho's arms at Chelsea.

"It's obviously good to be reunited with David Moyes," said Rooney, who had his "moments" with United's new leader during their years together at Everton but clearly finds him easier to work with than Sir Alex Ferguson, and suggests the new training regime suits his physique better. "He's a great manager and thoroughly deserves this job. It's good to work under him and hopefully we'll be successful together."

Moyes has clearly succeeded in coaxing a newly slimline Rooney into not merely proper fitness but also the best condition he has enjoyed for some considerable time. "I feel good," said a player who appears to have benefited from some "private" conversations with his manager during the course of a troubled summer. "I've had some good training the last few weeks. It's been stop-start with the injuries but I've just kept my head down and worked hard.

"I feel great. The training's a bit different under the new manager. I remember it from Everton – it's more intense. That's helping me. I feel good and am glad to be out playing.

"I've put my head down and worked hard and tried to do everything right. I've tried to show the right attitude. I've always felt that's a really important thing to do. That's paying off for me on the pitch. I feel fit and ready to do well."

Having scored his 199th and 200th United goals on Tuesday, Moyes believes Rooney can eclipse Bobby Charlton's record of 249 goals for the club. "It's always a challenge," said United's No10. "It's a massive football club and it's amazing how long that record has stood for. To be edging closer to it is great but I think the most important thing for me was to get back playing."