Former Celtic defender Mark Wilson warned Ronny Deila's men not to write off their Champions League opponents.
Wilson watched his old club draw 0-0 with Qarabag in Azerbaijan in the third qualifying round, progressing 1-0 on aggregate.
They now await Friday's play-off draw with Maccabi Tel Aviv, Astana, Partizan Belgrade, Skenderbeu Korce and Malmo the possible opponents.
"There's no doubt Celtic are the biggest name in the draw," said Wilson.
"You can't get too far ahead of yourself in this competition or you'll get stung. These teams are at this stage for a reason; they've got good players, okay they might not be household names but they're good sides.
"Celtic will know that, I don't think they'll take any of these teams lightly. Celtic will have to remain cautious, but they still remain favourites to go through."
Wilson was impressed with how the side equipped themselves in Baku, and said the fitness of the squad could be key this season.
He told BBC Scotland: "I was very impressed with them, I thought they were fantastic. Right from the goalkeeper, the back four, to that three in midfield who really sat and protected.
"There was no period of sustained pressure from Qarabag, but that was down to how Celtic defended. It was a really measured performance.
"Last night you could see the fitness. I don't think come 90 minutes in 40 degree heat they look tired at any stage and that was a lot of the chat before the game that Celtic were going to tire in this heat.
"I think they finished the game the strongest team and were probably unlucky not to snatch a victory in the end."