Mourinho is wary of the threat posed by Robins
The fear for Bristol City, when drawn at home to Manchester United in the Carabao Cup quarter-finals, was that the ambitious Championship upstarts would be distracted by their superstar visitors.
Four wins from their last four league games has silenced any talk of that. The Robins are in blistering form and they have needed to be, with Wolverhampton Wanderers and Cardiff City setting a frightening pace atop the division and City clinging to their coat-tails in third place.
And despite having his eyes on bigger prizes this season, namely the Champions League, where United will face Sevilla, Jose Mourinho is well aware of the threat clubs in the second tier can pose to teams like United if they take their foot off the pedal.
"For me now, the Championship is not the Championship of five or 10 years ago," said Mourinho.
"The Championship is now high-quality teams with lots of players that could be playing in the Premier League easily.
"So we need to take the game really seriously."
While United see the need to field a full-strength side if they are to reach the final four, the fact remains that injuries will continue to strip them of starters.
Serbian midfielder Nemanja Matic is likely to be rested after carrying a knock in recent weeks. Eric Bailly, Marouane Fellaini and Michael Carrick are all out too.
Which leaves Mourinho with a difficult decision in the centre of midfield, where he could start Paul Pogba, returning from a three-game suspension, or he could go to out-of-favour Armenian international Henrikh Mkhitaryan, with whom he had a training-ground row recently.
"I am going to make a few changes and it is possible Micki is involved," admitted Mourinho.
But Bristol City boss Lee Johnson knows that whatever XI United send out at Ashton Gate, it is likely to be filled with stars.
"We respect the fact they are going to have a world-class XI, whichever one they choose to put out," Johnson said.
"However, we are in good form, and I think the players' confidence is as good as it could be.
"I think we have a group that's very hungry to prove how good they are and it's a chance for the players, and the club, to enhance their reputations.
"For us there is minimal pressure involved apart from that which we put on ourselves to perform.
"I think this is a difficult place to play (for visiting teams), and it will be on Wednesday given the atmosphere.
"I know our fans and it will be an unbelievable atmosphere, and if we can get on the front foot, cause a few problems, then who knows?"