Buttler is a player who has been under fire but who could replace him and why has he not played well with only one century in 40 innings.
He has not played well due to his one day style, he needs to play his natural game not just block every shot. This is one of the reasons why Buttler fails to translate his white ball form into red ball.

Possible Replacements
Foakes – He has been a very good player for a number of years however his first class form has dipped a little in the last year . Test Average : 41.50. First Class Average : 38.01.

Bairstow – His test form might not be in the best of touch right now but he may still become a great wicket keeper. Like buttler he is a one day cricketer. Test Average : 34.74. First Class Average : 43.51
