Ferguson has been considering whether to play an extra midfielder against Pep Guardiola's side at Wembley on Saturday.
GEAR:Get your Manchester United home shirtwith Kitbag. Free delivery on orders over £40
But the Scot, seeking his third Champions League win in 12 years, is unlikely to flood his midfield and should stick with the 4-4-2 system which has brought a record 19th English title.
That would mean Mexico international Javier Hernandez, who has scored 20 goals in his debut season at Old Trafford, starting in attack alongside Wayne Rooney.
It would spell more Champions League disappointment for Scotland midfielder Darren Fletcher who started his first match since March 1 last Sunday after recovering from a virus.
Fletcher missed the 2009 Champions League Final when Barcelona beat United 2-0 through suspension and he was an unused substitute for the 2008 final in Moscow when Ferguson's side defeated Chelsea on penalties.
"It's not easy leaving players out because you are dealing with the human side of the game and players who have worked ever so hard all season for the team," Ferguson told a news conference on Tuesday.
"It's a squad game for us this year and it can't be easy. Unfortunately, there's one person that has to tell them and it's me.
"It's not an easy job but it has to be done. We have to win the game and they understand that. I pick a team for the right reasons and I pick the subs for the right reasons.
Ferguson said it was important to focus on what was best for United.
"It's not just about Barcelona, it's about us too, what's best for us and the best way of winning the match," he said.
"It will be down to how we operate the attacking part. It's not easy picking a team with the players I've got because they've all contributed and that doesn't make it easy for me."
