Liverpool already turned down a chance to get a much bigger gap, so they can't really afford to lose to Villa at this point, even a tie wouldn't be really ideal for them. They had a great season so far and I am pretty sure that we are going to end up with a much better situation here and could do a lot better on the long run as well. This is why I can see how Liverpool will put everything they have into this game and get a win.
Liverpool next game is against Manchester City not Villa, and just like you said they can’t afford to lose any more matches, the draw against their city rivals Everton has shorten the gap between them and arsenal and dropping points again after just a week will be very bad for the title contender.
Liverpool will play away in this game and it going to be a big challenge, Manchester city on the other hand are struggling and trying to get themselves together, they are in a fight for the top 4 and they will also fight for all 3 points. It going to be the match of the week and I really anticipate this one.
I think Liverpool might likely find it difficult to win Manchester city in this second leg, because considering their present performance now I don't really think if they would be able to win Manchester city in this game. Because in the first leg Manchester city was in misform, they were not consistent then. But with their recent form in the premier league right now I think they may likely get a secured a win or a draw against Liverpool.