Manchester United appear to have identified Eliaquim Mangala as their number one defensive target after sending a senior scout to watch the Porto centre-back.
The Frenchman is also believed to be attracting Premier League attention from Manchester City and Chelsea.
City pulled out of a reported £50m January transfer deadline-day double swoop for Mangala and his teammate Fernando, and their hesitation has allowed their neighbours to join the chase for his signature.
David Moyes is making plans for a Red Devils defence which is likely to be without both Nemanja Vidic and Rio Ferdinand next season, and according to The Telegraph, one of his leading advisers flew to Portugal to watch Mangala play 90 minutes in Porto's win over Gil Vicente on Sunday.
The 23-year-old has made 62 appearances for Porto since signing from Standard Liege in 2011.
