Date, time and coverage: Tuesday 5 November, 19:45 GMT. Live TV coverage in the UK on ITV. Follow the action live via ManUtd.com's rolling blog and MUTV Online's radio commentary.
Form guide: United will be feeling confident heading to San Sebastian after the 3-1 win at Fulham on Saturday extended the unbeaten run to seven matches. In recent weeks, David Moyes and his players have spoken about the need to build momentum with a string of victories; three points in the Anoeta Stadium will not only help that cause, but also move the men from Old Trafford one step nearer to qualification for the knockout stages. Real Sociedad, on the other hand, will be hoping to kick-start their own Champions League campaign having lost every one of their group-stage games to date. Domestically La Real are faring significantly better. Currently sitting in 5th place, they have only lost one of the last six games, a sequence that includes Saturday's 5-0 thrashing of Osasuna.
Ins and outs: The Reds' win at Craven Cottage on Saturday came at a cost as Rafael, Jonny Evans and Tom Cleverley all picked up first-half injuries - of that trio, only the latter made the trip to the Basque region. Sunday's crunch encounter with Arsenal could be another factor in Moyes' selection on Tuesday night. Meanwhile, Real Sociedad have a relatively full contingent of players at their disposal, although recently-arrived loanee Esteban Granero has been ruled out for six months after rupturing his anterior cruciate ligament.