Former skipper Paul Lambert says victory at home to Slovan Bratislava is a must if Celtic are to progress to the Champions League knockout rounds for the first time since season 2012-13.
Celtic begin their campaign in the tournament’s new format on Wednesday night against the Slovakian champions.
“I don’t think people should think it’s going to be an easy game,” Lambert told the BBC’s Good Morning Scotland radio programme.
“If Celtic underestimate them, it’ll be a sticky tie, but I don’t see Brendan Rodgers doing that.
“Celtic have got to get off to a good start.”
Lambert, a Champions League winner with Borussia Dortmund in 1997, says “without a shadow of a doubt” Europe’s elite competition has lost its way.
From this season, a new format takes hold with the structure of eight groups of four banished.
An expanded 36-team tournament will see each side play eight games – four at home and four away – in a league phase, against two opponents from each of the four seeding pots.
Lambert says it’s designed to “suit the elite clubs”.
He added: “The big ones will know they have time to catch up if they lose. It’s a bit over the top for me, it should be the champions or the top two that come in, but money changes the game, and that’s what has happened.”
Lambert does believe, though, it it is “easier to progress” in the new format, no matter the team.