Butland goes into the opening game against Italy as one of England's big hopes.
"If I didn't think (there was a goalkeeping place up for grabs), there would be no point. I'm not going to stand here and think three places are taken and just give up. I've got to prove that I'm good enough to go. I don't see the fact that I've come down to the Under 21s as a bad thing.
"Conversations were had and this is probably the best thing for my development. I know that going to the senior squad would be fantastic but in terms of game-time and getting that development it would be better to stay here. I feel really good in this squad and I feel part of it.
"But this is the step to the next level and I feel very confident that if I get the opportunity to have a good tournament, and then a good season next year - hopefully in the Premier League with Stoke - who knows? But that's the target - to go to Rio."