Celtic host Qarabag in a UEFA Champions League qualifier on Wednesday as they bid for a return to European football's elite.
Ahead of their third qualifying round tie with Qarabag, Celtic assistant manager John Collins says the Scottish giants must "earn the right" to get back in the UEFA Champions League.
Celtic missed out on last year's competition after losing to Maribor in the play-off round, going on to reach the last 32 of the Europa League instead.
Azerbaijan's Qarabag visit Glasgow for the first leg of their tie on Wednesday and Collins is under no illusion as to the importance of making a return to European football's top table.
"We know how important the Champions League is - for the whole country - but especially for us," Collins is quoted as saying by BBC Sport.
"We've had success in it before and that's where we want to be. All the teams want to be in the group stages, we're no different.
"But we've got to earn the right, and to earn the right you've got to play well and make sure there's 100 per cent concentration from the first minute to the last minute.
"That's key at this level. You can't switch off. You switch off and most of the time you get punished."
Celtic were comfortable 6-1 winners over Stjarnan in the last round, but Collins is taking nothing for granted against Qarabag, who edged Montenegro's Rudar Pljevlja 1-0 to progress.
"They're a good football team," he added. "They like to pass the ball, [and have] good movement throughout their team.
"[They have] a couple of Brazilians that are very dangerous, one up front, a striker Reynaldo and a midfielder who knows how to pass the ball.
"They're a good all-round team. I would say definitely a Champions League standard team.
"It's a step up from our last opponents, a massive step up. We'll have to play well if we're to get through but we're capable of playing well that's for sure."
Ronny Deila's Celtic could be without Charlie Mulgrew after the midfielder picked up a knock in a friendly against Rennes over the weekend.comments