Lennon furious at late penalty decision.
The Hoops got off to the perfect start when midfielder Ki Sung-yueng scored from the spot in the third minute after striker Gary Hooper had been fouled by Lars Joel Ekstrand, although the official took his time before pointing to the spot.
With four minutes remaining, and Celtic looking as though they had done just about enough to get past a youthful and inexperienced Italian side, Yildirim adjudged Hooper to have fouled Neuton Sergio Piccoli in the box.
Almen Abdi sent Lukasz Zaluska the wrong way with his penalty to leave the stunned home side with one point from two games.
The Celtic manager was in no doubt as to why they his side had not come away with all three points ahead of their trip to Rennes next month.
"It was a disgraceful decision," he said.
"Gary Hooper did what he could do to get out of the way.
"Ours was definitely a penalty but the referee deliberated for 20 seconds before giving it. I can't understand that. Hooper is very upset and angry as all the players are after putting so much work in to the game.
"To lose two points after a decision like that is hard to take for the players. Of course it will (affect our chance of qualifying). It denied us two points when we wanted to enforce our home advantage."
Celtic's Charlie Mulgrew reacts angrily last night