Ronny Deila's side crashed to an embarrassing 4-1 defeat to Legia Warsaw on Wednesday night to leave the Hoops with a mountain to climb if they are to reach the Champions League play-off round.
Deila admitted a fortnight ago that qualification for the money-spinning group stages this season was crucial to his transfer plans as he looks to bolster his Hoops ranks.
He has added just keeper Craig Gordon and Cardiff's Jo Inge Berget to his squad this summer and fans have criticised the lack of big-money buys ahead of the crucial Euro qualifiers.
Hay said: "You have to wait and see the outcome of the tie. You could talk about [the lack of signings] now and Celtic end up getting through.
"The time to discuss that is after the outcome and after we know if Celtic have made the group stages or not.
"If you do it now and Celtic win next week, you have jumped the gun. The time and place to criticise or make comment on the strategy … is after we know how they have progressed in the Champions League or Europa League.
"Ronny has been with the squad for a short time but has worked with them a lot … he will know where Celtic have to go. He can't sign anyone to play next week anyway so there is no point making snap decisions."