Maguire became the most expensive defender in the history of the game when he completed an £80million move from Leicester last month and the 26-year-old has started all four of Uniteds opening Premier League matches.
Victor Lindelof has played alongside Maguire throughout and the pair impressed on the opening weekend as United kept their first clean sheet since February in a 4-0 victory over Chelsea.
However, the Red Devils have conceded a goal in every game since and Maguire has faced some criticism for his displays at the back.
Asked by Premier League Productions to rate Maguires start in United colours, Sherwood replied: Average. I dont think hes been great but I dont think Man United have been great.
I dont think its about individuals at the back, its about partnerships and him and Lindelof havent been good enough.
Sooner or later theyre going to have to work on that on that training field and get a partnership.
All the best centre half partnerships are not always necessarily the two best players. Its the two that can work together better.
At the moment I think their understanding is not correct. Theyre not covering around each other enough.
Dimitar Berbatov believes this weekends clash with Leicester will be particularly difficult for Maguire, but has backed United to come away from Old Trafford with three points.
United have a tough match against Leicester at Old Trafford on Saturday, the ex-United striker told Betfair.
It could be a particularly difficult one for Harry Maguire who joined them from Leicester in August.
Playing against your old club is s***. Its very difficult to spend two seasons somewhere – as Maguire did at Leicester and I did at Spurs – showing what you can do then get a big move and have to play against your old teammates with whom youre probably still in touch.
As hard as you try to be professional, friendships can sometimes get in the way.