Manchester United have joined the growing number of clubs closely monitoring the Porto defender Eliaquim Mangala as they plan ahead for the gradual easing out of Rio Ferdinand and Nemanja Vidic.

While the Premier League champions will return to the business of trying to bolster their midfield in the January transfer window, possibly renewing their interest in Ander Herrera of Athletic Bilbao, the manager, David Moyes, and the chief executive, Ed Woodward, have also had internal discussions about bringing in a new centre-half next summer.

Ferdinand will turn 35 in November and, with his well-documented fitness issues, United are acutely aware the former England defender could be in his final season at the club. Vidic, 32 next month, is a sufferer of long-standing back problems and, while Phil Jones, Chris Smalling and Jonny Evans are all highly regarded inside Old Trafford, part of the thinking is that all three have a habit of missing chunks of the season through injuries of their own. Despite their support for each player, United believe they might need to bring in someone else to make the handover from the Ferdinand-Vidic era as seamless as possible.

United have not fully ruled out Ferdinand staying another year but, as it stands, they consider it unlikely and the club's scouting staff will be regular visitors at Porto matches this season to compile detailed reports on Mangala.

Mangala, a France international of Congolese descent, signed for Porto from Standard Liège two years ago and has established himself as one of the outstanding young centre-halves in Europe. A strong, physical player, renowned for his aerial ability, the 22-year-old was particularly influential in Porto's successful defence of the Primeira Liga last season.

However, he would not be cheap and there promises to be strong competition. Mangala has a €45m (£37.8m) buyout clause in his contract and is also reputedly on the radar of, among others, Manchester City and Chelsea. Monaco asked about him in the summer but valued him more around €35m (£29.5m) and, with Paris St-Germain also interested, there are several clubs in the reckoning that have the financial strength to outdo United if it came to a bidding war.

Mangala recently parted company from his agent and there is a feeling in Portugal that he is likely to end up with Jorge Mendes, the so-called "super-agent". Mendes's involvement would almost certainly signal this is Mangala's last year at Porto and, beyond that, it potentially becomes a question of politics as well as money. Mendes, whose list of clients includes Cristiano Ronaldo, has strong relations with United, particularly the former manager Sir Alex Ferguson, but also represents José Mourinho, as well as having a direct line into just about every major club in Europe.