The striker was not included among the 22 players heading to Sardinia, where the Nerazzurri will look to return to winning ways after being held to a 3-3 draw by Fiorentina on Sunday.
Icardi has not played for the club since being stripped of the captaincy and has now missed their last four matches in all competitions.
The Argentina international had complained of a knee problem, but club medics appeared unable to find any significant problems when conducting tests last week.
The 26-year-old has been heavily linked with champions Juventus amid reports he has played his last game for Inter, although his agent and wife Wanda Nara insists he is happy to stay at the club.
Head coach Luciano Spalletti was unwilling to discuss the forward's situation.
"Many things have already been said about Icardi by [chief executive Giuseppe] Marotta and [president Steven] Zhang," said the coach.
"From now on I'll only talk about the players that are available for selection, not those who aren't, because they're the ones who are on the field and care about the fate of Inter.
"I won't talk about the others anymore."
Inter is third in Serie A after 25 games, 22 points behind leader Juve.