David Moyes believes Wayne Rooney has rediscovered his hunger and desire at Manchester United and insisted he would never attempt to curb the aggression in the striker's game.

Rooney will shoulder even greater responsibility for United on Wednesday when they face Bayer Leverkusen without the experienced spine of Robin van Persie, Michael Carrick and Nemanja Vidic. The penultimate test in the Champions League group stage comes with Rooney's temperament under scrutiny having kicked Jordon Mutch during United's draw at Cardiff City on Sunday.

The 28-year-old was shown a yellow card by the referee Neil Swarbrick at Cardiff – his last red card for United came in 2009 – where he also scored his eighth goal of the season at club level. Moyes attributes the England international's fine form to a renewed commitment at Old Trafford, and welcomed the occasional show of aggression from the forward.

"It's a big part of his game," said the United manager. "He's an aggressive player, he plays with his heart, as well as the skills he's got in abundance. That's a big part of what he is. That's the way he was when he was a boy at Everton with me. A lot of people said that might have been missing from his game last season – it's certainly not missing now. He's got the hunger back and the desire back and he's committed for everything. I'd rather have a Wayne Rooney that way than any other way."

The United manager accepted Rooney may have been fortunate at Cardiff but has no intention of trying to change the player's game at this stage in his career. Moyes added: "I think his form and attitude and temperament have been first-class. I couldn't fault any of them. But there will always be times when players have little bits when they don't always quite go for them, and on that occasion Wayne was probably a little bit fortunate. I don't want him to change. But I still think the referee made the right decision in his call.

"I want Wayne to have fire in his belly. I think he plays better when he's tough and aggressive. I don't want to change Wayne Rooney, that's for sure. I don't want him to be kicking at anybody, but I want him aggressive, challenging and full of running. And I think at the moment we're seeing a really good Wayne Rooney who's in top form and scoring goals as well."

United would qualify for the knockout phase with victory in Germany – as would Sami Hyypia's Leverkusen – while both teams can progress with a draw should Shakhtar Donetsk lose at home to Real Sociedad. "The group is very open and we had a great opportunity to pull away further at Real Sociedad, but we didn't, so we have a big game now," admitted Moyes. "We want to get the job done before the final game but we know we have a tough game."

Van Persie remains sidelined with toe and groin problems, Vidic with concussion, Carrick an achilles problem and United also have Marouane Fellaini suspended due to his late dismissal at Real Sociedad. Phil Jones has been struggling with a groin injury suffered on England duty but has travelled to Germany. "Their team is strong enough to compensate for those losses," said Hyypia, who is keen to avenge a 4-2 defeat at Old Trafford in the opening group game. "We have always played well at home," the Finn added. "It won't be easy for Manchester United and, of course, we really want to win. It's not just an important game for us."

Hyypia has overseen Leverkusen's best start to a Bundesliga season with 10 wins from 13 games and the club can boast eight consecutive home wins in the Champions League group stage, a run that includes their 2004-05 and 2011-12 campaigns. The midfielder Sidney Sam has been a major influence with 11 goals in all competitions but will miss United's visit with a thigh injury suffered against Hertha Berlin on Saturday.

Moyes said: "Sami was a very good player for Liverpool. They had a very good team at the time. He is doing a very good job. They have a very good team in a strong league. It's a European tie away from home and we had a good result at home against Leverkusen but it's important we get a result of sorts to maintain our good position in the group."