The Argentine was ruled out for up to three weeks after injuring his thigh in the 2-0 league victory over Almeria last Saturday.
But despite the loss of Messi, and a reported defensive crisis with Javier Mascherano, Jordi Alba and Carles Puyol missing, Lennon is not expecting his side to see much of the ball against the Spaniards.
"It is obviously very good news for us that he is out because he is the best player in the world, but our approach will be the same whether he played or not," he told Sky Sports News.
"However, it is tinged with sadness because it is always fantastic to see the great players play here in Glasgow.
"Barcelona don't change their system, they don't change their style of play and 4-3-3 is just what they believe in. It has worked well for them very well over the years.
"They are supposed to have defensive problems through injuries, but they seem to keep on having clean sheets.
"They never conceded against Vallecano, Sociedad and Almeria so regardless of the personnel they are still defending very, very well."
However, Lennon, who led the Hoops to a memorable 2-1 victory over Barca on their way to the final 16 last season, admits his side may struggle to match the visitors for possession.
"It does help if you can get the ball off them and have a sustained period of pressure," he added. "But we will look to try and exploit any weakness they may show on the night.
"It will be very much at times containment, to limit Barcelona to as few chances as we can and at the same time maximise the opportunities that we get, as we did last year."