Empoli clinched a 3-2 victory on Sunday.
“We were too distracted and allowed Empoli far too much space," Gasperini told Sky Sport Italia.
“It is a serious incident. Ilicic and Papu Gomez had been the most positive in the game until that moment. He's in great shape right now, so losing him for both this and the next game is stupidly negative for us.
“We didn't have the intelligence or the strength to follow up our recent results. Perhaps this is what happens when in Bergamo they talk about pushing for a Champions League place. It doesn't reflect our status or our capabilities right now."