GETTY
Championship City welcome Jose Mourinho's star-studded Premier League outfit to Ashton Gate for an 8pm kick-off.
Despite the calibre of their opponents, home boss Lee Johnson says promotion from the second tier rather than Wembley glory is on his mind.
"If I was given a ticket to win either the United game or Saturday's match at QPR, I'd opt for the latter - but on Wednesday the super-competitive side of me will take over," he said.
"When Man United come to town, I think it always brings that feeling of it being a big tie, and this club hasn't had it for a long time, probably back to people like Brian Tinnion, that iconic goal against Liverpool.
CARABAO CUP DRAW: WHEN IT IS MADE AND HOW TO WATCH
"The players have got to feel somebody could be that hero in this game."
Mourinho is wary of the quality the Robins have.
"For me now, the Championship is not the Championship of five or 10 years ago," the United boss said.
"The Championship is now high-quality teams with lots of players that could be playing in the Premier League easily.
"I'm making a few changes for the match, not many, because Bristol City are one of the best teams in the Championship."