The Rossoneri will have to make do without their first-choice right-back in Wednesday's Champions League match versus the Catalans
The defender picked up a muscular injury in training earlier this month and Milan were initially hopeful that he would be back in time for the game at San Siro.
However, the Rossoneri have now confirmed on their official website that the Italy international has been left out of the 20-man squad for the home game against Barca.
Abate is likely to be replaced by either veteran full-back Gianluca Zambrotta or Daniele Bonera in Wednesday's encounter.
The highly anticipated quarter-final clash kicks off at 20.45CET. The return leg will take place on Tuesday, April 3.