Javier Hernandez netted a brace against the Portuguese side, and Ferguson admitted that the strikers is just one area where he could move things around.
"[Javier Hernandez] is improving all the time. He trains magnificently and he has great enthusiasm," said Ferguson. "I must say he has got me thinking. I have got him, Wayne Rooney, Robin van Persie and Danny Welbeck, and I don't know what to do with them.
"We have to look at the big picture – Rio [Ferdinand, rested this evening] with his age and a big game against Chelsea on Sunday. Then we play Chelsea again midweek [in the League Cup] and Arsenal again on the Saturday.
"We have a massive programme and it is important to utilise the squad we have. We have got injuries and putting Michael Carrick [at centre-back] is not the best but we had to do it."
The Red Devils have won all three of their games in Group H so far this season.