Former Celtic and Scotland goalkeeper Alan Rough believes that Bhoys fans will not be happy with the shape of the squad at Parkhead.
Celtic opted against making big signings in the transfer window last summer, but shocked supporters by selling striker Moussa Dembele to French club Lyon on transfer deadline day.
Brendan Rodgers was busy in the January window as he sought to beef up his squad in light of a serious challenge from rivals Rangers, but Celtic focused on short term loan deals as Jeremy Toljan, Timothy Weah and Oliver Burke arrived on agreements running until the end of the season.
Celtic have just announced a net profit of £15.2m for the first half of the season and have £38.6m in the bank.
And Rough thinks Celtic fans will be looking for the club to spend to bring the squad up to the standard it was in years past.
"I don't think too many Celtic fans will be happy with the squad as it is just now", Rough said on PLZ Soccer.
"If you look at it now, it's not a Champions League squad, not by a million miles, compared to the players they had.
"So I'm sure the supporters will be looking for some kind of investment to get back into the Champions League because that's where they want to be.
"To do that you need to spend money", the former goalkeeper added.
Celtic missed out on making the Champions League group stage this season, but are still involved in the Europa League.