United boss David Moyes is expected to overhaul his squad this summer after a disappointing first season in charge at Old Trafford, with a number of players likely to arrive at the club at the end of the season.
Bosnian international Pjanic was a target for the club in the January transfer window, with Moyes still looking to improve his central midfield options even after last summer's £27.5m capture of Marouane Fellaini from Everton. Pjanic, 23, is expected to star for Bosnia at the World Cup, and would be a great addition to the Red Devils midfield with his blend of dribbling and outstanding technique.
Meanwhile, the departure of Nemanja Vidic to Inter Milan at the end of the season - and the expected loss of Rio Ferdinand - leaves one, and possibly a second gaping hole in the Manchester United backline, hence their interest in Moroccan international.
But they may end up with neither after Spanish press revealed that Barcelona have eyed up a swoop for the duo, with a potential €40m double deal on the cards.
Benatia would slot into the defence with Carles Puyol set to leave the club at the end of the season, whilst Xavi is 34 and won't be able to carry on at such a high level for much longer, causing them to look in the direction of Pjanic.
Last summer was a huge disappointment for United as they failed to land some of their primary targets, and whilst the capture of Juan Mata in January has renewed hope that United can still compete with the best, their hopes of landing Benatia and Pjanic have taken a hit with Barcelona's interest.