Sir Alex Ferguson confirmed the news during his weekly press conference at Carrington, but also offered some positive news by stating his belief that Jones “should” start training next week and that Nani's injury suffered against Chelsea is not as worrying as first feared.
"We only have the two injuries thankfully,” the boss told reporters. "Nani came off against Chelsea last week. It is not serious but we will keep him out for a couple of weeks.
"We thought it could have been another bad hamstring injury. It is a slight one. He won't be ready for Sunderland but certainly the game after that.
"Phil Jones is not back yet. We will be a lot fresher tomorrow. We have done well in training this week. Hopefully we will be OK. Jones should start training next week. He is coming on.”
The match with the Royals offers United a chance to maintain and possibly enhance a 12 point lead at the top against a team currently without a manager after Brian McDermott was surprisingly relieved of his duties on Monday.
Despite this, Sir Alex is taking nothing for granted and is braced for a tough test against the relegation candidates, though he admits the decision to sack of long-term boss McDermott has left him bemused.
"I always consider every game hard at this time of the season," the boss explained. "Reading are fighting for their lives at the bottom of the league. It is possible they could come here without a manager.