Louis van Gaal reportedly sent a Manchester United scout to run the rule over Sporting Lisbon defender Paulo Oliveira earlier this month.
Currently, Van Gaal has Chris Smalling, Daley Blind, Phil Jones, Marcos Rojo and Paddy McNair as central defensive options, but the latter three of that quintet have all suffered with injuries over recent months.
As a result, Van Gaal has considered bolstering his options during the January transfer window, with 23-year-old Oliveira among his list of targets, according to The Mirror.
The report adds that Van Gaal had the Portugal international watched during Sporting's 2-1 victory over Rio Ave on September 19 - a game in which he played the entire 90 minutes.
Oliveira joined Sporting on a five-year deal from Vitoria Guimaraes in 2014 and went on to make 40 appearances in all competitions last term.
