Both first legs turned out to be closer than expected, with out-of-form United holding reigning champions Bayern to a 1-1 draw at Old Trafford and Atleti coming away from Camp Nou with the same scoreline.
Goal selects the best imagery from the evening's fixtures ...
Old Trafford showed a united front as it braced itself for the visit of Bayern
Barca suffered an early setback when Gerard Pique fell awkwardly and had to be substituted
Bayern players surrounded Antonio Valencia after he picked up a yellow for a foul on Philipp Lahm
Atletico faced the tough task of keeping Lionel Messi quiet on his home turf
They were dropping like flies as Diego Costa was next to be replaced
It was later confirmed that the Spain international had suffered a hamstring injury
Danny Welbeck was put through just before half-time but the striker failed to beat Manuel Neuer
At half-time Pep Guardiola had plenty to ponder as he headed down the tunnel at Old Trafford
On 56 minutes the Nou Camp was silenced by a stunning goal from Diego
The Theatre of Dreams was bouncing on 58 minutes when Nemanja Vidic headed home
But Bastian Schweinsteiger equalised less than 10 minutes later
The midfielder wheeled away to celebrate with the away supporters
The Barcelona crowd were pacifed on 77 minutes when Andres Iniesta slipped Neymar through ...
... and the Brazilian found the far corner with the aid of a slight deflection
Bayern's night ended on a sour note as Bastian Schweinsteiger received a second yellow