Celtic were given a "masterclass" and "a taste of their own medicine" as they crashed to a 5-0 loss to Paris St-Germain, says John Collins.
Brendan Rodgers' side suffered their heaviest European home defeat in a one-sided Champions League contest.
"It was a joy to watch for everybody that appreciates great football," said former Celtic midfielder Collins.
"They did to Celtic what Celtic do to near enough every other Scottish team week in, week out."
Neymar, Kylian Mbappe and Edinson Cavani, twice, were on target for the French visitors, with Mikael Lustig knocking in an unfortunate own goal.
Rodgers, who has overseen an unbeaten domestic run of 53 games, was dismayed by a poor first-half display, saying "we played like under-12s at times".
- Match report: Celtic 0-5 PSG
- We played like under-12s, says Rodgers
- Uefa charges Celtic for fan invasion
- Ralston vows to learn from Neymar joust
Collins, 49, was also critical of the home side's approach, while admiring the skills of the expensively assembled visitors.
"It was tough for Celtic but you've got to learn from these teams," he said.
"Celtic started very poorly, they kept giving the ball away. They could hardly get a kick and I think that was a real shock to their system.
"In Scotland, they get time on the ball and teams drop off them. Whenever Paris lost the ball, they won it back straight away.
"They don't get that challenge in Scotland, it's so difficult for them to adapt to not having the ball for long periods. When you don't have the ball, you get tired because you're doing a lot of chasing.
"When they did win it, there were slack passes and that seemed to spread throughout the team in the first 15 minutes. When you give it away to good teams, it takes a long time to get it back."
PSG's star-studded forward line provided the goals at Celtic Park but Collins, who spent two years playing in France with Monaco, highlighted the contribution from midfield.
"People will talk about the front three but I thought the middle three, Adrien Rabiot, Marco Verratti and Thiago Motta, were exceptional.
"Celtic could not get near them. Their one-touch passing and movement in tight situations was a joy to behold."
Bayern Munich beat Anderlecht 3-0 in the other Group B game, with Celtic travelling to Belgium next.
"The target [for Celtic] is third place and they will be in a battle with Anderlecht," added Collins.
"They sold their better players in the summer, they're not of the same quality as Bayern or PSG. But Celtic will have to play well over those two games to have a realistic chance.
"The passing needs to improve - when the ball went wide to Patrick Roberts and Scott Sinclair they were trying to run with it and dribble. PSG were doubling up on them and taking the ball right back.
"As a winger, you can't always run with it. Can you keep it?
"It will be a shock to Brendan and his players - they set high standards. But they got off to a shocking start in the last campaign [a 7-0 loss away to Barcelona] and they grew into it and got better."