Celtic manager Brendan Rodgers urged his side to learn from their 5-0 thrashing by Paris Saint-Germain two weeks' ago ahead of Wednesday night's away fixture with Belgian side Anderlecht.
The Hoops are an impressive 57 games unbeaten domestically but were embarrassed by PSG's deadly front three - Kylian Mbappe, Edinson Cavani and Neymar -at Celtic Park two weeks ago.
"Games like the PSG one are little reality checks. That's what it's like at this level. Even after the game against Rangers on Saturday we reflected on it and looked at things we could have done better," Rodgers told reporters.
"It's boys who are used to winning and when you come up against that level of play at the very top level of the game then it's tough and it's humbling.
"We didn't plan and focus on being that timid in the PSG game. But this is a level where you are learning all the time. Just because we've been on the run we've been on for the last 15 months or so doesn't mean you're not susceptible to such performances."
Last season Rodgers's side went all six games without a win in the competition's group stages.
