Cape Town - Juan Mata scored the only goal of the game as Manchester United got revenge on Manchester City with a 1-0 win in the EFL Cup fourth round at Old Trafford on Wednesday.
The first-half was played at a lively tempo but both teams struggled to find their passes, with United particularly wasteful in possession.
City saw more of the ball and they threatened after just two minutes when Jesus Navas got away down the right flank before sending in a dangerous cross that Kelechi Iheanacho headed over from inside the six-yard box.
However, there was very little goal-mouth action in the opening 45 minutes, although the closing stages brought some excitement to the Old Trafford crowd.
Luke Shaw combined well with Marcus Rashford on the left flank in the 36th minute before the left-back picked out Paul Pogba with a cutback and the Frenchman touched the ball to Zlatan Ibrahimovic, whose first-time shot from the edge of the area was deflected over by Nicolas Otamendi.
Two minutes later, Pogba sent in a low cross towards Ibrahimovic, but Willy Caballero raced out to get a glove in before the Swede, while at the other end Marcos Rojo got in a vital block on Iheanacho after a loose pass from Daley Blind had let the Nigerian in on 40 minutes.
The Red Devils made a better start to the second-half and they almost found the opener on 49 minutes when Ibrahimovic played Pogba through on goal, but the midfielder's shot from eight yards out on the left was tipped onto his near post by Caballero.
The home fans were celebrating five minutes later as Mata fired United in front - Ibrahimovic latched onto Rojo's ball over the top and he squared the ball to the Spaniard, who directed his shot into the bottom left corner from 10 yards out.
A sustained spell of pressure from the Citizens saw Aleksandar Kolarov lash over from range on the left in the 63rd minute, but Ibrahimovic should have extended the hosts' lead moments later at the other end when was picked out by Rashford's cross from the left, but the striker failed to connect from six yards out.
Kolarov was presented with another chance on 70 minutes when City won a free-kick, but he fired over from 25 yards out on the right.
United absorbed quite a bit of pressure from their noisy neighbours in the final 20 minutes, although Caballero had to be alert in stoppage time as he raced out to deny Pogba, who was sent through on goal by Ander Herrera.