Sunderland are reportedly keeping a close eye on Austrian international duo Aleksandar Dragovic and Martin Hinteregger.
David Moyes has endured a tough start to life since taking over at Sunderland, having conceded 13 goals in seven Premier League games as they sit bottom of the table.
The Scot is understood to be hoping to add defensive reinforcements in January in order to address the leaky backline and boost their chances of survival.
The Black Cats held on to Lamine Kone over the summer and brought in Papy Djilobodji from Chelsea, however, Moyes feels he needs more options.
Reports claim that Sunderland sent scouts to Vienna to watch Dragovic and Hinteregger feature for Austria in the 2-2 draw with Wales on Thursday.
Dragovic and Hinteregger both moved clubs in the summer to Bayer Leverkusen and Red Bull Salzburg respectively, and the Premier League outfit will have work hard to convince them to leave so quickly.