Former Manchester United defender Denis Irwin wants to see the club add cover to their defensive ranks this summer.
Nemanja Vidic and Rio Ferdinand have left the club for Inter Milan and Queens Park Rangers respectively, and with new boss Louis van Gaal adopting the 3-5-2 formation at Old Trafford, Irwin feels that his old side need to bolster their ranks.
He told the club's official website: "It has been good to see young Michael Keane and Tyler Blackett come into the defence and get some game time too [in pre-season], but I think it's an area we may have to strengthen through the transfer market to give us more experience.
"I think the manager now has a better gauge of the formation and the defenders he has to play in it. I do think some of the defenders need to work on the vocal side of their game. Jonny Evans is vocally strong but a couple of the other lads are a little bit quieter.
"One of them will have to take control and move people around. I'm sure that will come and I'm sure the manager will have encouraged them to be vocal. Any new system needs that but it comes with experience, too. When you're younger, you keep your head down a bit and get on with your game."
A recent report claimed that Van Gaal is looking to complete a £40m double swoop for Arsenal's Thomas Vermaelen and Roma centre-back Mehdi Benatia.
