The Swedish side has already played 17 games in their domestic season and Lennon was impressed with what he saw when they took on Atvidaberg at the weekend.
"You are talking about the Swedish champions here," Lennon said.
"They have international players and international-calibre players. They are 17 games into the season so they are match-sharp and a good side.
"They pass the ball very well and are very well-organised. There is a good blend of youth and experience in their team, and on the back of winning the title they come into the season confident.
"I think they are putting more emphasis on qualification for the Champions League at the minute than probably their own progress in the league, so they are very dangerous opponents.
"It will be disappointing if we don't make it. Our whole emphasis on preparation for the last few weeks has been on trying to negotiate these ties as best we can. I think we have enough quality in our side to give them plenty of problems.
"I wouldn't say I'm relaxed but I am aware of the situation now. I suppose it's coincidental we have a Swedish team again. It was two tough ties against Helsingborgs last year and I would envisage it would be the same again against Elfsborg."