James McPake reckons Celtic are a tougher nut to crack than Rangers with their intensity giving Ange Postecoglou's side the edge.
The former Dundee boss lost his job last month with Mark McGhee drafted in as his replacement.
The timing was peculiar after back to back wins but McPake still had time to lead his team out twice each against the Glasgow giants.
McPake's Dundee side lost all four - although ten goals shipped over two games against the Hoops hinted at who they had a tougher time against.
And the former boss says he's in no hurry to face off against them again, admitting they're a tougher test altogether than Rangers.
He said on Go Radio: "To differentiate both teams from managing against them, the first time we went to Celtic Park when Ange was just there, it hadn't quite clicked.
"Kyogo made his debut and they beat us 6-0. I don't remember that one very well...but they were great that day and you could see something was building.
"The Rangers game under Steven Gerrard, we had to change and give them all the respect they were due.
"I believe we were very unlucky. Jason Cummings missed a penalty and we had double the shots on target of Rangers that day, but they won the game, so fine.
"The game when Celtic came to Dens, they killed us again. They scored the early goal, then they got another one, and they were relentless.
"You've no chance when they do that. You think you've got a chance, then they come out again at the start of the second half.
"That's one thing I noticed about Celtic: they're very aggressive at the start of both halves, and they're ultra-aggressive once they get a goal."
McPake admits Gio van Bronckhorst has improved Rangers since he took the reins and the Dutchman is still hopeful of clawing back the three-point gap on Celtic.
And McPake is impressed with some of the changes he has made including Glen Kamara being deployed in a higher role for their Scottish Cup victory over Dundee at the weekend.
But he still feels it's Celtic who have more to offer.
He went on: "Giovanni van Bronckhorst, he changed it about and that day they cruised past us 3-0. They were very comfortable.
"He made it different, and watching it on Sunday he had Glen Kamara playing further up the pitch in the No.10. He's noticed something in Glen that he wants to use.
"Having worked with Glen, he's a much better player when he's further up the pitch and he can score goals as well. He's good at that end of the pitch even though he hasn't scored many for Rangers.
"But if I was to pick one I wouldn't want to play against - the two of them would beat us! - but Celtic have been the ones that we really struggled against."
