Sir Alex does not anticipate making wholesale changes to his line-up for the Champions League tie with Otelul Galati on Wednesday.
The Reds have five points from three games in Group C and will be looking to complete the double over the Romanian champions, even though they have acquitted themselves well in all of their matches despite competing at this level for the first time.
Wayne Rooney's penalties secured a 2-0 victory in Bucharest and, with home advantage, United will be looking to move on to eight points and close on a place in the knockout stages.
"I don't think there will be a lot of changes," revealed the boss. "Maybe two or three but no more.
"We have to win on Wednesday, without doubt. We're at home and I expect us to win and, if we do that, it's in our hands when we play Benfica at home.
"I expect Benfica to beat Basel as they're in a bit of disarray with Thorsten Fink going to Hamburg. We'll hopefully win our game and, when we play Benfica at home, it'll be the decider in our section."
Sir Alex acknowledges Galati are awkward opponents, who posed plenty of questions for the United defence in the 2-0 triumph earlier this month.
"Having watched them, I knew nobody turns them over," stressed the boss. "Their games against Basel and Benfica had been tight and they were exactly that way against us. Galati set out their stall to make sure they weren’t going to be embarrassed.
"They were well organised, really determined defensively and they got stuck right into us. Some of the tackles in the second half were very aggressive. It made it a difficult type of game but I think we improved enough after half-time to be the better team.