Icardi finished the Serie A campaign with 29 goals, taking his overall tally in the league for Inter to a century, but was not named in Sampaoli's final 23 for the tournament in Russia.
The 25-year-old was overlooked again following the injury sustained to Manuel Lanzini, with Argentina instead calling-up Enzo Perez to replace the West Ham midfielder in the squad.
Despite his incredible form at club level, Icardi has earned just four caps for Argentina, but Zanetti believes he will earn more chances in the coming years.
"Mauro Icardi deserved an opportunity for what he did and what he has been doing. I would have liked him to be with us in Russia," Zanetti told reporters.
"He is very young and has a lot of future ahead of him. He will have the opportunity to be part of the Argentine National Team."
Argentina struggled in their opening Group D match at the World Cup, seeing Lionel Messi have a penalty saved in a 1-1 with tournament debutants Iceland, and Zanetti spoke of his nation's difficulties in the build-up to Russia 2018.
"I do not know if the discussion around Argentina should be about if they have enough as it's just a different stage. This team has great players," he added.
"You have to give it time because the qualifiers were difficult and there was a change of coach."