United have endured a torrid week, losing their last three matches in all competitions, but according to the Manchester Evening News, Mourinho will have to stick his current squad for the time being.
His predecessor, Louis van Gaal, did not bring in new names during his two-year stint. Although goalkeeper Victor Valdes arrived as a free agent.
The last time the Old Trafford club bought in the winter window, was in 2014, when Mourinho who was Chelsea boss at the time, allowed Juan Mata leave Stamford Bridge. The Spanish midfielder was snapped up for a then United record spend of £37m by manager David Moyes.
United have spent over £450m on rebuilding the squad since Sir Alex Ferguson retired in 2013, but have only won the FA Cup since that time.