Ferguson favoured a diamond midfield during his 32 month spell in charge of Rovers and has kept faith the the variation of 4-4-2 since returning to Peterborough for a third spell a fortnight ago.
But McCann revealed his squad have been prepared for a number of potential options which Ferguson may choose.
“Since Darren has gone in, he's changed it to a diamond which he played a lot here,” McCann said.
“Whether he comes with a diamond here we'll see. Lee Tomlin is suspended so it might change things.
“We've prepare for one or two ways he may go so nothing is a surprise to us when we see the team on Saturday.”
McCann has spoken of his respect and gratitude towards Ferguson, under whom he played the best football of his career at Peterborough and began his coaching career with the London Road club’s U15s before progressing to manager himself.
And he praised his opposite number for the groundwork he laid at Rovers before his surprise resignation last summer which paved the way for McCann’s reign at the Keepmoat.
McCann said: “I spoke about it at the start of the year that he laid the foundations with a lot of these players that had probably only played one year at League One.
“Speaking to the group, they felt they could have done better in the league last season.
“It was a good club to come into, everything was set.
“We've made our changes in terms of the staff.
“I don't know the reasons why he left, that's nothing to do with me.
“I was focused on coming here and getting a reaction from the players and making them better than what they are.
“I think we've shown that.”