Despite scoring 29 goals in 36 appearances for the Serie A outfit this season, Icardi was one of eight players cut from Argentina's 35-man preliminary squad for the summer tournament.
However, in his press conference following the announcement, Sampaoli was confident he had picked the right players for Russia.
He told reporters: "We arrived at this number after much analysis of each position. We are clear that these players are the ones who are nearest to the idea of play we are trying to implement.
"The selection of the players has to be comparative with the respective upcoming tournament."
Turning his attention to specific players, Sampaoli added: "I decided on Cristian Ansaldi because he is a full-back who can play on both sides.
"Sergio Aguero is back working normally since last week. Gabriel Mercado will not have any kind of issues. We will see how Lucas Biglia arrives.
"I have spoken with Lionel Messi and he is very excited for what is coming. Physically he's in great shape at the moment".
However, the head coach refused to comment on Icardi's snub, raising further doubts of a rift within in the Argentine camp.