The classy centre-back had only recently returned from a different problem with his groin, suffered while representing France, when he was forced off during the Reds' 2-2 draw at Atalanta in the Champions League.
It has led to another untimely spell on the sidelines for the defender, who accepts he is needing to adapt to the rigours of life in the Premier League after switching from Real Madrid in the summer.
However, he acknowledges this is something he is addressing, in order to get back to helping United on the pitch.
"Yes, I’m working very hard and, you know, footballers are like F1 [cars] so sometimes we have to change something and to improve the motor," he told club media at Carrington.