Manchester United boss Jose Mourinho is in the dark over the extent of Marcos Rojo's injury suffered in the win over Reading.

The Argentinian has been in outstanding form of late but was replaced by Phil Jones only 19 minutes into the FA Cup tie, even if the Reds were already two goals to the good at the time.

With Tuesday's EFL Cup semi-final first leg against Hull City on the horizon, followed by the Premier League showdown with Liverpool the following weekend, Rojo's fitness will need to be assessed.

Mourinho told : "I don't know [what the damage is]. We have to wait a little bit. A muscle is a muscle and you're always afraid of it but let's see what is going on.

"It would be so important for us to keep our central defenders fit for the month of January. But I prefer to wait. Chris Smalling and Phil Jones did a very good job for us."