Juan Mata struck to win a tight Manchester derby as United knocked out EFL Cup holders City 1-0 to reach the quarter-finals.
The Spaniard pounced to drive low into the corner from Zlatan Ibrahimovic’s pull-back as United set up a home tie with West Ham.
City boss Pep Guardiola made nine changes to his side, who are now six games without a win in all competitions – his worst run as a manager.
Their best chance arrived early on when Kelechi Iheanacho headed over from six yards, while second-half substitutes Raheem Sterling and Sergio Aguero made little impact.
Victory was United’s second in five matches, and only Jose Mourinho’s fourth win in 18 meetings with Guardiola.
Other EFL Quarter Final Fixtures
Liverpool vs Leeds United
Hull City vs Newcastle United
Arsenal vs Southampton