Manchester City manager Roberto Mancini believes Manchester United's 15-point advantage in the Premier League is a consequence of teams' "very soft" mentality against them.

United go into Monday night's Manchester derby unbeaten in the league since 17 November, winning 25 of their 30 games, whereas City have won seven matches less in what has been a meek defence of their title.

Mancini complimented United on their aura - a staple of the club's success under Sir Alex Ferguson the past 20 years - but felt opposition teams had gone easy on them.

"No one plays well against United because they only play with fear," the Italian said. "Every team that plays against United plays very soft because they think this game is difficult, they can't beat them.

"It is not true - if you play strong against United you can beat them, like they can beat us. We are young as a team and we don't have the same importance like United in this moment."

Despite United's machine-like charge to a 20th championship, Mancini's reluctance to accept he is culpable in City's disappointing season - which also saw them eliminated from the Champions League at the group stage - is a recurring theme.

He has publicly blamed several players this season, most notably Joe Hart and Samir Nasri, yet has not issued a mea culpa for Mario Balotelli's detrimental effect before he was sold in January.

Mancini has spent £291.75m since his arrival at Eastlands in December 2009, yet at his Friday press conference again bemoaned football administration officer Brian Marwood's failure to lure Robin van Persie to the champions in the summer.

robin van persie manchester city

Van Persie reacts after scoring the winner past City in December

Ferguson, whose decision to part with United's recent trend of buying players aged under 25 in order to sign Van Persie from Arsenal has proven to be critical, was keen to stress the Dutchman was never going to City.

Asked if the Blues would have been in a more competitive position had they bought the 29-year-old striker, Ferguson replied: “It’s hypothetical, he was never going to City."

“He’s been fantastic for us, a really good footballer.

“We needed a bit of maturity up front and he’s been terrific.

“The improvement is not just through Robin but even when he doesn’t score he’s a fantastic footballer.”

City return to Old Trafford for the first time since their 6-1 evisceration of United in October 2011, while the Reds will have fonder memories of Van Persie's stoppage-time winner in the atmospheric 3-2 victory in December.