The squad were put through their paces in the Manchester sun before embarking on a trip to the Romanian city of Cluj.
Sir Alex's men face CFR Cluj at the CFR Stadium on Tuesday night in the second Group H game of the season, having kicked things off on a positive note last month with a 1-0 over Galatasaray at Old Trafford.
Ahead of the visit to Romania, the Reds look set to be without Antonio Valencia and Michael Carrick, who both missed training on Monday. Ashley Young trained alongside one of the physiotherapists but is not expected to travel.
The players were joined by a familiar face for Monday's session, with former defender Mikael Silvestre returning to hone his fitness. He will not be rejoining United.
View a gallery of photos from training by clicking on the image above.