United, who begin their defence of the Premier League title at home to Birmingham on Sunday, have adopted a 4-4-2 formation throughout pre-season after largely relying on a 4-3-3 set-up last term.
Ronaldo's goal threat and his ability to perform on both flanks and through the middle prompted Ferguson and former assistant Carlos Queiroz to adopt the 4-3-3 formation at the start of the 2007-08 campaign, which resulted in United winning the league and Champions League.
But Ronaldo's £80m exit has forced a rethink at Old Trafford, with Ferguson and his players repeating the importance of being more 'compact' this season.
Pre-season performances have lacked the cavalier displays that were often typified by Ronaldo, but Fletcher - set to captain Scotland in their World Cup qualifier against Norway on Wednesday - claims that United will continue to be attack-minded even without the talents of Ronaldo.
He said: "We've always been tight as a team and we have a great defensive record to back that up. Maybe we have been a little bit too expansive in the past, though.
"But the Manchester United ethos is all about attacking football. That's what the fans expect and we will continue to honour those principles.
"You can't be wide open all the time, though. You have to be disciplined and I think you will see a much more rigid 4-4-2 formation this season, with the ability to go 4-3-3 when needed.
"Cristiano is a great player, an unbelievable player, and he was a major part of our success here.
"But it's a team game as well and a lot goes into a winning team. We still have the nucleus of that, but we've also added players like Michael Owen and Antonio Valencia.
"They have both looked really good in pre-season. Michael has scored a few goals and Antonio's performance against Valencia last week was fantastic, so we feel like we have added a bit of quality as well.
"With Wayne Rooney
, Dimitar Berbatov, Michael and Federico Macheda competing for places up front, it looks promising for us up front."
Fletcher is expected to be a key figure in midfield for United this season. The continuing absence of Owen Hargreaves due to injury and Fletcher's impressive contribution last season have ensured that the 25-year-old is now one of Ferguson's most trusted midfielders.
The Scot's inability to play in the Champions League Final defeat against Barcelona in Rome due to suspension has been suggested as a major factor behind United's defeat.
And Fletcher admits that missing out in Rome has actually helped raise his reputation outside of Old Trafford.
He said: "It has been nice to hear that it might have been different had I played in Rome and that's been the only thing anybody has ever said to me all summer, that I might have made a difference.
"I was desperate to play in the Final, but you have to give credit to Barcelona because they put in a fantastic performance on the night. We were beaten by the better team.
"People talk about Rome and the fact that I couldn't play because of the suspension, but sometimes you become a better player some people's eyes when you don't play.
"I feel as though I am right in there and fighting for my place in the starting line-up now, though. But I know that I can't take anything for granted because you only have to look at the quality of the players who can come in.
"Last season was a big step for me, though. There are some great midfielders at the club, but I managed to start the season and stay in the team for the majority of it.
"My performances improved because of the continuity that comes with playing most weeks."