United will need to overturn a 2-0 deficit from the first leg and know their task could become immeasurably harder if Liverpool score an away goal, as that would require the hosts to net four times. Van Gaal is not concerned, though, per the club's official Twitter feed and James Pearce of the Liverpool Echo:
The Dutchman called for his players and the fans to believe they can win and said the supporters will have a significant bearing on the game, per United:
Per the Mirror's Jacob Murtagh, the 64-year-old is well aware the team needs to improve on their poor performance at Anfield. He said: "The first half was not our half. We have to do much better than that, otherwise we cannot win."
According to the Times' Paul Hirst, he added the club owe it to the fans to produce the result they need:
Thursday's game will be a significant milestone for Van Gaal, his 150th match in UEFA competition.
According to Murtagh, he cares far more that United win: "It’s a lot, yes? It’s much more important we beat Liverpool tomorrow. That is our aim. When we can do that with two goals difference and without conceding, then we have extra-time and, with our fans, we can make it."
Van Gaal also gave the latest team news ahead of the clash, per United:
However, he would not be drawn on whether Marouane Fellaini would feature after the Belgian was jeered by some of his own fans on Sunday.
Per Murtagh, Van Gaal said: "I cannot say if Fellaini plays tomorrow because then I give away part of my lineup and I don’t want to do that. But Fellaini has his way of playing and he can give us a lot of qualities and has contributed in a lot of games in a very good way."
Ander Herrera was also present for the press conference, and he too accepted a big turnaround was needed:
The Spaniard also stoked the fires with a parting shot at Liverpool, per BBC Sport's Juliette Ferrington:
Van Gaal was evidently pleased with the midfielder's comments, per the Press Association's Simon Peach:
United do indeed need to produce a much better showing than their listless performance in the first leg, in which the Reds probably could and should have put the tie to bed completely with another goal.
Overturning a two-goal deficit at home certainly isn't inconceivable, particularly with Van Gaal's strong record against Liverpool—the first leg was the first time he'd failed to beat them in five attempts—but it does require a significantly improved performance.
The Reds will know they can kill off the contest with an early goal at Old Trafford, but should United score early, it will set the remainder of the game up to be a thrilling contest.