Gaz retired in 2011, Rio, Vidic and Evra retired or left the club in 2014. We're now in 2016 and apart from RB (whom ironically was sorted by a right winger), none of the 3 roles had been adequately filled. Sure, people will say that the defence is stable and will bring stats as proof to back it up. However these people ignore that we had 3 of the most defensive minded managers that had ever lead Manchester United. People who believed that closing the gaps is the foundations of a winning team.
That's not good enough. The best teams in the world used to rely on their defences and the best defences had players whom you could rely on week in week out. SAF was not a defensive sort of manager but even he insisted on that. Parker-Bruce-Pally-Irwin, Gaz-Stam-Johnsen-Irwin, Gaz-Rio-Vidic-Evra. Those were the defences that lead us to the peak of England's and Europe's greatness. Sure players in midfield and the forward line may change. Who will forget Ole-Sheringham replacing Cole-Yorke in the dying moments of the CL final which made history. But the defence was always the same, a rock United to lean on, a bastion even the young Barcelona team struggled against.
So Mou has every right to demand and fully expect his defenders to do well week in week out. No ifs no buts. And considering that they have failed miserably in replacing Vidic, Rio and Evra then he's got every right to add new players who will. Sure Smalling and co are still relevant. No team can only have 12 players these days. But from now on nothing will be guaranteed for them, they have to work hard in the training room and make the most out of every minute on the pitch.
We've got a manager who goes past the names. He showed that with Mkhitaryan. For example Blind was flawless yesterday. People like Shaw should better watch out as hype alone can only get you so far with this manager around