Jose Mourinho has the German international as his No 1 choice recruit - but privately behind the scenes at United, there are fears over a permanent contract for a player with a chequered history of injuries.Boateng, 29, suffered muscle and tendon injuries over the past three Bundesliga campaigns, missing 27 games in total since December 2016.Last season he suffered a hamstring injury in April, almost causing him to miss Germany's dismal World Cup campaign in Russia.Boateng also missed a number of games at the beginning of the 2017-18 season due to another hamstring problem.

He returned to training last month - starting on the bench in Wednesday's friendly against FC Rottach-Egern - and remains contracted to Bayern until 2021.

But with the transfer window closing at 5pm on Thursday, Mourinho is running out of time to find a new central defender.