The left-back was transferred from United to the Portuguese giants last year, and his development has attracted attention from top clubs across Europe, such as Real Madrid and Barcelona.
Manchester United boss Erik ten Hag has confirmed they have a buy-back option in their deal with Benfica for Alvaro Carreras.AdvertisementAdvertisementTen Hag revealed on Friday: "We are monitoring the progress of Álvaro Carreras at Benfica, we have a buy-back clause. We loaned him to Preston, to Granada, he didn't play much there... and we had the opportunity to sell him.
"But we have a buy-back clause that allows us to control the situation. We are the ones who control the situation. We have to evaluate the situation, to see if it can be an option for us, we have a specific clause.
"But playing at Manchester United is not that easy, it takes time. You have to develop."