Strachan – who worked with McCann at Peterborough United – left his role as assistant manager as the new manager was appointed on Wednesday evening.
The move came as a surprise with the Rovers board initially keen to retain all backroom staff that worked under previous boss Darren Ferguson following the Scotsman’s resignation earlier this month.
But McCann says the move arose due to a combination of his desire to bring in his own man plus Strachan’s personal wish to leave.
“I have a good relationship with Strachs,” McCann said.
“When I left Peterborough he was one of the first people to ring me.
“I think it was down to him having to get up really early in mornings and he’s loyal to Darren, which I can understand in football.
“Also I wanted to bring in my own number two any way.
“I wanted to do that before and the board knew that.
“It was regardless of Strachs, if I could get who I wanted in somewhere.
“It made it a little bit easier for me.
“It’s disappointing to see a good man leave in Strachs but I’m sure no doubt him and Darren will be at a very good club in the near future.”
McCann declined to reveal who he will be appointing as his assistant but expects the new addition to join the staff for next week’s training camp in La Manga, Spain.
“We’ve got it finalised from the club he was at,” McCann said.
“The players will certainly love him.
“He’s passionate, a good coach and one who the players will respect a lot.
“And he’s different to me.”