Manchester United have reportedly sent their scouts to watch Benfica duo Enzo Pérez and Nicolás Gaitán with a view to a move during the January transfer window.

According to talkSPORT, the Argentine duo were watched by the Red Devils' scouts during the Portuguese club's cup game against Braga which they lost 2-1.

Louis van Gaal is eager to strengthen his team during the upcoming transfer window despite spending over a reported £150m during the summer to bring in the likes of Ángel Di María, Marcos Rojo, Daley Blind and Radamel Falcao among others.

Earlier in the season, there were reports suggesting that the United manager will be given an unrestricted budget to strengthen the team and get them back to winning ways. Now with the run of form taking them ever closer to the top, the manager believes that the club are right back in the hunt for the title along with league leaders Chelsea and Manchester City.

Gaitán has been linked with the Old Trafford club since the summer, with United even trying to engineer a swap deal for the Argentinean using former player Bebé, but it was rejected by the Portuguese club.

Apart from Van Gaal's team, Premier League rivals Liverpool are also interested in the former Boca Juniors player and could battle United for his signature during the winter transfer window.

Gaitán's compatriot Pérez has also been on the 20-times champions' radar and the former Bayern Munich and Barcelona manager could make a double swoop for the duo in January.

Argentine midfielder Pérez also confirmed the Red Devils' interest during the summer transfer window, but apart from the Premier League club, La Liga side Valencia have also shown interest, and with billionaire Peter Lim backing them, they will have money to spend to challenge United for the player's signature.