Celtic goalkeeper Craig Gordon has warned against thinking that the Glasgow side are already through to the Champions League group stage.
The Scottish champions are favourites to progress after a 1-1 first-leg draw away to Maribor in Slovenia.
But Gordon told BBC Scotland: "Their style of play is they play a lot on the counter-attack.
"The away leg could suit them so we have to be very wary - it's not over and done with yet."
Callum McGregor gave Celtic an ideal start with what could prove to be a vital away goal after only six minutes.
Damjan Bohar equalised eight minutes later, but Celtic manager Ronny Deila expressed himself satisfied at returning to Scotland with a draw, although his players felt they could have won the game.
"We are a little bit disappointed we did not go on and win the game - we had the chances to do that," said Gordon.
"But 1-1 is a good away result and we'll take that back to Celtic Park and look to build on it.
"They tried to put us under pressure and they were pretty good on the counter-attack themselves.
"There's still a big game to play and one we'll have to be very careful with."
Celtic only reached the play-off stage after Legia Warsaw were thrown out of the competition for fielding a suspended player near the end of their win over their second leg against the Scots.
The Poles had inflicted a 6-1 aggregate defeat on the Scots, who had conceded four in Warsaw, but Delia's side did not adopt such an attacking style away from home this time.
"I think we lost the goal against the run of play at the time having started really well," said Gordon.
"We lost a bad goal, but at least we steadied ourselves and got back into the game.
"We definitely were not as gung-ho after we lost the goal and learned our lesson, although we still managed to create a few chances.
"But, overall, it's a pretty good evening's work. It was a good match with chances at both ends."
Maribor coach Ante Simundza thinks his side can still beat Celtic over the two legs.
"We wanted a positive result and we got one," he said. "We are still in the tie.
"Celtic were very solid in the first-half, but we dominated the second half and I think the draw was fair.
"The result gives an advantage to Celtic with the away goal, but we did equalise very quickly and we have to be satisfied."
Celtic defender Mikael Lustig was frustrated that Celtic are not in a better position for next week's second leg.
"Before the game, we would have thought 1-1 was a decent result, but the feeling right now is that, if we had put a little more quality into their box, we could have scored at least three goals," he said.
"We felt we were the better team, but in the second half we did not play like we should but still managed a couple of good chances and could have been given two penalties as well.
"If we don't manage to get through this, we don't deserve to be in the Champions League."