After being thumped by Manchester United, Wigan Athletic boss Roberto Martinez fired a warning at Manchester City.
Martinez feels Roberto Mancini's men face a far more considerable test of their mettle over the next few months.
"They adapt to adversity. You can see everyone taking responsibility and using that to get a result.
"That is the biggest strength they have had for 25 years.
"That is why any team that wants to win the league, beyond any sort of money, or any sort of players you want to bring in, need to beat Manchester United mentally.
"That is the biggest battle.""What Manchester United have is that mentality," said the Wigan chief.