Manchester United are trying to solve their issues with new players as it seems. Their priority must be the midfield and attacking line for sure. de Jong addition would be very helpful for the team in not only defense but also offense. However this might be an easy deal for them at all. They tried to make this transfer happen before but they couldn't meet the price Barcelona demanded.
Now maybe they might add him to the squad easier than before. Because his market value has dropped significantly since last summer. Honestly I wouldn't leave Barcelona if I were him.

He will need to be patient to see Manchester United reaching a high level of performance.