Butler rejected the offer of a new contract at Rovers and opted to join League Two side Scunthorpe United on a one-year deal.
McCann says he is comfortable with the move which leaves him with Tom Anderson and Joe Wright plus youngsters Shane Blaney and Rian McLean as centre back options as he heads into the summer.
"I've got the improvement in young Shane Blaney and I'm sure you'll see a lot of him this year," McCann said.
"We've got Joe Wright coming back in for us and I've said before I think when he's fit that he's one of the best in the league.
"Tom Anderson is improving all the time and he's going to be top drawer for us this year.
"Plus we will add another one into that area.
"I'm quite pleased."Young Rian McLean, the lad we brought from non-league, the fans haven't seen him yet and he;s been working hard for the last six months.
"He's coming on leaps and bounds.
"I'm quite comfortable with the situation and I was never going to held to ransom on it."
McCann paid tribute to Butler on his departure, saying: "Buts has been a tremendous servant to the football club.
"He had a tremendous year last year and we want to thank him for his efforts.
"As it is in football, you move on."