A 3-3 draw meant Celtic can only reach 99 if they beat Dundee United after being presented with the league trophy on Sunday. St Johnstone were a goal up after a poor first half from Celtic, but the champions recovered to take a 3-1 lead before conceding twice in the final six minutes.
Lennon picked a half-strength team which then received a half-time dressing down. "It was unacceptable. Miles off the level we've been at. And I'm not just talking about the players that came in either. Some of the players who were playing on a regular basis weren't at it.
"I wasn't happy with our defending for the final two goals either. I thought we were lazy. But I can't be too critical of my players. Since we won the league. We've won five and drawn two so they've kept their momentum going. It was an opportunity to rotate the squad and that's what we've done. We've had a look at some players and we've learned something again. We were poor in the first half but very good in the second. Am I frustrated we can't get 100 points? Not really."
His counterpart Tommy Wright confirmed that striker Stevie May - taken off in the first half with a shin injury - was okay. "He's fine. He took a nasty one and has stud marks on his shin but there's no problem with him. We will think about whether to play him on Sunday because we can still finish fifth. I am delighted with tonight. I thought in the first half we were excellent. The reaction to keep going right to the end meant the players got what they deserved in the end."