Callum McGregor's goal in Slovenia gave the Scottish champions a slender advantage ahead of the home leg, making them the bookmakers' favourites to reach the group phase.
"We were well prepared and the players were fantastic for 90 minutes," BBC Sport quotes Deila as saying.
"We looked like a team, worked hard together and created chances. It's a good result but we could have won it."
The Bhoys coach went on to say that he has "a good feeling" about Celtic making it through the qualifying stage of the competition.
Celtic were reinstated into the Champions League despite losing 6-1 on aggregate to Legia Warsaw in the previous round, after the Poles were found guilty of fielding an ineligibility player.