That’s what Juan Mata has claimed despite Jose Mourinho’s men flying high in the Premier League this season.
United have overcome Burton Albion and Swansea to reach the quarter-finals stage of the Carabao Cup.
And they go into this week’s showdown with City off the back of successive top flight wins over Bournemouth and West Brom.
United will be expected by many to sweep Lee Johnson’s team aside as they look to retain the first trophy they secured under Jose Mourinho.
However, Mata reckons the Robins, who sit third in the Championship, will pose a threat to the Red Devils.
“This week we also have a ‘double session’, what else could it be?” he said on his personal blog.
“We have the Carabao Cup on Wednesday against Bristol City.
“They are having a sensational season in the Championship so far, and with a few consecutive wins lately they have proved to be one of the candidates to get promoted.
“It won’t be an easy game.”
Next up for United in the Premier League is Saturday’s trip to the King Power Stadium to take on Claude Puel’s Leicester.