London: Manchester United do not know when Argentine defender Marcos Rojo will be available again after he missed the 3-0 win over Liverpool on Sunday, manager Louis van Gaal said.
Van Gaal told reporters the 24-year-old, signed from Sporting Lisbon in the close-season, was injured in training on Saturday, which meant Phil Jones was brought in despite only just being back from injury.
The manager declined to go into detail, saying only: "I don`t think it`s healthy but I`m not a doctor."
United were already without injured defenders Rafael, Chris Smalling and Luke Shaw, which meant fielding a three-man backline of Jones, Jonny Evans and midfielder Michael Carrick.
Meanwhile Liverpool`s Australian goalkeeper Brad Jones, brought in for a first league appearance since March 2013, will stay in the side in place of the out-of-form Simon Mignolet.
Manager Brendan Rodgers told reporters the change was for "an indefinite period", adding that Jones will play in the Capital One Cup quarter-final away to Bournemouth on Wednesday.