Stoke City stopper Butland has not yet given up hope of being selected for the games against Tunisia, Panama and Belgium, but he will give his full support to Pickford - or indeed Pope - if Southgate leaves him on the bench.
"You are all in the same boat," he told reporters. "Whether you play or whether you're on the bench, or however it may be, at some point in your career you will be one of those three roles.
"You will either be a young, up-and-coming goalkeeper watching the experienced one; you'll either be on the bench or you'll be in goal yourself.
"It's important that you're humble and that you're respectful and you put all pride aside. Whoever gets selected can't succeed without the support and backing of the other two.
"Regardless of what happens, I want to be part of a successful England team and if I have to swallow my pride and disappointment at not being the number one, then I've got to do that for us to be successful and obviously to help whoever is in goal perform at their best."
Butland played a little over an hour of England's 2-0 friendly win against Costa Rica on Thursday evening, before being replaced by Pope for the remainder.