Luke Shaw, 23, would see his current deal expire next summer, so a new contract is necessary if the left-back is to stay at Old Trafford for the long-term.
Despite struggling with injuries and for regular starts in previous campaigns, Shaw has seen his first-term chances improve exponentially under Jose Mourinho this season.
Having impressed in recent games, the left-back has earned a recall to Gareth Southgate's England squad.
Shaw joined the 'Red Devils' from Southampton in 2014 for around £27m.