There's more to Manchester United than Robin van Persie insists Alex Ferguson

Sir Alex Ferguson today predicted that both Wayne Rooney and Javier Hernandez will score 20 goals this season, as he reflected on the comeback from last season's title disappointment which has put his side top of the Premier League and into the last 16 of the Champions League.

The Manchester United manager insisted that the team were not at risk of becoming too reliant on Robin van Persie, who already has 11 goals to his name heading into tomorrow's match at Villa Park."I don't think [over reliance on one player] has been a problem in the past. Last year we lost [the title] on goal difference. I don't expect us to lose on goal difference again," said Ferguson, for whom Jonny Evans is a doubt for tomorrow with a groin strain sustained in Wednesday's win at Braga.

Ferguson said van Persie had "come to us at the right time, there's no doubt," after the loss of the title to Manchester CIty. "He's experienced," he said. "Eight years at Arsenal helps. Chicharito is on six goals. He is getting back to where he was a couple of years back and I'm certain he will get 20 goals plus. I think he is enjoying himself. This summer's rest has helped him immensely. Wazza will get there too. Wayne will get to that 20 goal target too. That's a healthy situation we have got there."

During today's press conference it was revealed that Nani will be out for ten days with a hamstring strain suffered in Portugal in midweek.

Ferguson said that Aston Villa's frequent change of manager may be the cause of their struggles to reach the standard of the 1980s. "They have a great history," he said. "It's probably correct to say that they haven't matched their expectations over the years. The year we won the league [1993] they had a good team. You wonder when managers change whether that has bigger effect than the playing standard of the team. They've had quite a few managers - Brian Little, John Gregory, Martin O'Neill, Alex McLeish - that's quite a collection of managers they've had over the years."

Of Wednesday's laboured 3-1 win over Braga, he said: "We found the game difficult. It was an indication of how teams prepare - they sat back. The pitch was soggy, it was a strange stadium, one end a huge rock, the other a grassy knoll. We just never made anything of the game at all. They say back." When the floodlights failed around the hour mark United were 1-0 down. "At that moment I thought it was very difficult for us," Ferguson said. "We put van Persie on, he got us a goal and it made them come out. From that moment on there was only going to be one winner."

United's progress means they have no worries competitively in the week before they play Manchester City next month at the Etihad, while Roberto Mancini's side travel to Dortmund with their participation in this season's European competitions at stake. "It's a good position to be in and hopefully we can capitalise and utilise our squad," the manager said. "It gives me good opportunities to alter and give people that need a rest a rest but we still want to win the games. Galatasaray and Turkey [in two weeks' time] is always a difficult match and the last home game also. I just think that it's a good position to be in. Last season we went to the last game and didn't qualify and it definitely has an impact."