"It's now quite clear I have a major rebuilding job on my hands," said Calderwood, whose side has slipped to ninth in the table.
"The performances we are producing right now aren't good enough for Aberdeen Football Club. We've set high standards but they have slipped drastically and I won't settle for second best.
"You learn from every game and it's now apparent we need to make big changes. Playing at a great club like Aberdeen comes with extra expectation levels.
"It takes a certain person to handle that and sometimes some individuals can only go so far as a player. Maybe a few have been punching above their weight but are now being found and when that happens it's time for surgery.
"I'm preparing for a massive turnaround and it's looking like I'll be into double figures in terms of the number of departures," added Calderwood.