Mancini: United's attack is now the best in the world

Manchester City begin their Premier League defence against Southampton tomorrow, with their manager, Roberto Mancini, stating that rivals Manchester United have the edge going into the opening weekend.

United unveiled Robin van Persie as their star signing yesterday, with Mancini labelling the strikeforce at Old Trafford as not just the best domestically, but in the world.

Although there was obvious interest in Van Persie from City, he explained that buying the Dutchman would have made it tricky to keep his forwards happy given competition for places. However, the Italian now believes the quality at the disposal of Sir Alex Ferguson makes United the title favourites.

"I think they [United's strikers] are the best four in the world," he said. "Last year, our strikers did better than others, but if you want to do better than last year you have to work harder. Without Van Persie they were two yards ahead. Now with him, it is four or five."

It is clear that Mancini is aware of the danger that if the club does not strengthen when on top they could fall behind the teams around them

That was at the crux of his complaints about the lack of transfer market movement a fortnight ago, with Brian Marwood, the sporting director, bearing the brunt of his frustration. Mancini now cuts a far more relaxed figure after finalising the £15m transfer of Jack Rodwell from Everton.

"I don't have a problem with Brian," he said. "When you are the manager you want to know that you can buy a player quickly but at the same time it is difficult."

One player Mancini is hoping to sign is Athletic Bilbao's midfielder Javi Martinez, but he accepts that they face competition from a number of other clubs vying for his signature.

"We talked about Martinez with his club but it isn't an easy situation because there are three or four top clubs who want him," he said. "Sometimes it isn't enough to have the money to spend. When there are other top teams after a player it is difficult."

He also admitted that there is "no chance" of landing either Daniel De Rossi, the Roma midfielder, or Daniel Agger, the Liverpool defender.

Mancini is not too concerned because he is aware that it is Chelsea and United who have to play catch-up – hence their summer spending – because the champions are now the team to beat.

"The second year is difficult because the other teams going for the title buy new players and the other teams, maybe not the ones challenging for the title, want to beat you," he said. "It is important that we start the season very well."

Despite the relative lack of transfer activity, City's squad is one which is still improving and evolving - something which Rodwell was keen to point out.

"I'm going to feel my way into it and see how it goes," said the England international. "I'm here to improve and push myself, The players I'm training with are going to improve my game."

His manager believes Rodwell's key asset is his versatility. "Jack is for now and the future," said Mancini. "He can play in different positions and can improve a lot. It's important to put a player like Jack into the squad because he is young and can play in different positions. It's good for the team."