People were saying exactly the same thing prior to the game last December. We failed to win the game. And then we were 3 wins away from winning absolutely everything.
The game on Saturday is very important, for it is a derby, but it won't decide our season. United aren't particularly strong now, but they are much stronger than teams like Wigan or Norwich who have beaten us over the last 3-4 years. In one game anything can happen: OGs, red cards, deflections, penalties, brutal refereeing mistakes, etc. The more important thing is what happens over 38 games. Still, we can be optimistic, for Pep's record at Old Trafford is generally excellent: he has 5 wins there.
The key to our league season is to find consistency and go on a winning run, say 12 wins from 15 games. Then everything will be in our own hands. Will be very hard to win 4 titles over 5 seasons, though.