The Argentina international was a key player last season, but suffered a cruciate knee ligament injury in the Europa League win over Anderlecht in April.
However, he now appears very close to first team action - and though Jose Mourinho claims he won't feature in the Champions League clash tonight, he could figure in the next two weeks.
The United players were snapped taking part in an unusual hand-holding drill last night, as they look to make it three wins out of three in Group A.
In contrast, Benfica have had a nightmare start to their European campaign, losing at home to CSKA Moscow and then getting spanked 5-0 away to Basel in Switzerland.
The match in Portugal kicks off at 7.45pm this evening.
CLICK THROUGH THE GALLERY ABOVE TO SEE UNITED TRAINING AT THE ESTADIO DA LUZ.
