Jose Mourinho ramped up the pressure on referee Michael Oliver ahead of the Manchester derby, calling on City's tactical fouls to be stamped out in Sunday's clash.
Mourinho's Manchester United host Pep Guardiola's runaway leaders hoping to eat into their eight-point advantage at the Premier League's summit.
City have only failed to win once in the league so far this season, scoring 46 goals in 15 games in a blistering start to their campaign.
Though Guardiola has courted fulsome praise for his attacking tactics, Mourinho manoeuvred in typical fashion before the derby, highlighting what he perceives to be an uglier side to their game, having earlier accused City of routine simulation.
"It is a strategy that City have," Mourinho said. "They put lots of players in attacking areas and when they lose the ball, they can be unbalanced in terms of numbers.
"They have lots of people surrounding the ball area and they have a very strong – and this is a great quality – transition in the next few seconds.
"After they lose the ball, many times they need what is called a tactical foul.
"Then it is up to the referee to analyse and to make a decision about it.
"My answer always has to be the referee has to do his job – but I cannot speak about the referee."
United have won each of their last four Premier League games, the upturn in form coinciding with Paul Pogba's return from injury.
The France star is suspended on Sunday, however, and Mourinho suggested that the midfielder's absence could prompt United to alter their gameplan.
The Portuguese said: "There was a Manchester United with Paul, there was a Manchester United without Paul and we have another Manchester United with Paul.
"He is a player that has an impact in our style of play. That is obvious and now for the next three matches we have to cope without Paul and we have to try and win matches without Paul. It's not pessimistic. It's just a different way to play."
