Promises to be a great game.
I expect United to set the stall out very defensively in the first half of the first leg, playing the usual 4-5-1 away from home in Europe.
My starting line up would be :
Brown, Vidic, Rio, Evra
Rooney, Carrick, Scholes, Hargreaves, Giggs,
utilising the experience of Scholes and Giggs in the first half. Scholes, in the twilight of his career needs legs longside him in midfield, hence Carrick holding, and Hargreaves playing box to box.
Depending on how things are going, I'd use Anderson for Scholes, Nani for Giggs, and possibly Tevez coming on as well, either on 50 minutes if things have gone very wrong, or after 60 minutes if it is still 0-0. I believe the added urgency and mobility of those 3 players can make a huge difference against a team which may feel that they have us figured out. All 3 have shown the ability to be impact players when used as subs.
While Evra has been the best left back in the league this season, Hughes exploited his 1 obvious weekness at the weekend: his lack of height. Pushing Santa Cruz out right and playing high diagonals was a tactical master stroke by Sparky. Against Barca however, it'll be the dribbling skills of Messi which Evra will have to deal with... one of Evra's strengths.
I can't really call it. I'd expect at a maximum 1 goal each in Barcelona, although Puyol being missing may be a pivotal point. 1-1 would be a superb result for United, IMHO. 2-1 and we'd be through.
It should be good.