Ferguson named Nemanja Vidic as new club captain last week.
"The subject of picking a captain was straightforward," he said. "In the last two or three years Gary Neville has been the club captain, but as we know, he has had injuries so there is an inconsistency as to when he is in your team. For that reason we had to look elsewhere.
"We need a captain who will play every week. Because we have so many options in midfield, from time to time we change it around.
"With Nemanja Vidic, he just signed a new contract in the summer and will play all the time. If he is fit, he plays."