Neil Lennon reckons it is a matter of time before Celtic or Rangers smash the "glass ceiling" and reach the final eight of the Champions League.
The former Parkhead boss expects one of the clubs to finally achieve a spot in the quarter-finals in the future but admitted it might not be in the next "three of four years".
And Lennon is confident that even if that lofty goal cannot be achieved then both clubs should aspire to deep runs in the Europa League after Rangers reached the final two seasons ago.
"Well, Rangers proved that two years ago," said Lennon of the Glasgow clubs aiming for deep runs in the Europa League. "That will whet the appetite of Celtic as well.
"The glass ceiling for us all has been the last 16 [of the Champions League]. I think eventually someone will come along and break that and get into the last eight.
"Whether it happens in the next three or four years, who knows. I think it is always possible if you get the right draw and the right blend of squad at the right time.
"Certainly, the Europa League is one Celtic and Rangers could go far in. I'm still not convinced on the Conference League, what it actually is.
"I've watched a lot of games, and even the qualifying games, and I'm still not sure what its reason to be is but I do think that certainly they should be looking at the Europa League as somewhere they can go far in the competition."
Celtic and Rangers were both eliminated in the group stage of the Champions League last season but Lennon insists making the knockout stages and last 16 of the competition is "doable".
And he reckons the lure of Champions League football was the main motivation for Brendan Rodgers to return to Celtic.
Speaking on PLZ Soccer, he said: "Gordon has done it twice, I've done it myself, it is doable. It took me a couple of years to get that team together. Gordon built a team that got in twice. It's doable.
"The last 16, can you go last eight that has to always be the target for any ambitious club such as Celtic - and obviously they have got an ambitious manager in Brendan.
"I think the main reason he has come back is for the Champions League."
