Hayes has been on top form in the Europa League so far, taking his ability to cut through opponents' defences from Scotland to Europe with ease.
Manager Derek McInnes will be disappointed with the news of Hayes' injury, but has bolstered his forward line with Jayden Stockley, Miles Storey and Wes Burns coming in during summer.
The Dons have experienced travel problems in the build-up to tonight's massive fixture, but McInnes, whose side were held to a 1-1 draw in the first leg, told RedWeb yesterday that the delay shouldn't affect his plans.
“We weren’t planning on training at the stadium tonight anyway,” he said on Wednesday.
“We wanted to be a bit more specific and train here this morning so there is no real change from that other than the players will arrive in Maribor a bit later, we will get to the hotel just in time for dinner.
“The plans tomorrow will be as normal so there is not any real change to our preparations, truth be told.”