Neil Lennon described Celtic's performance as "immature" and "wasteful" after Dave Mackay scored St Johnstone's first Clydesdale Bank Premier League goal of the season to give the Perth men their first win at Parkhead in 13 years.
Peter Enckelman saved Kris Commons' spot-kick in the third minute to enrage the Hoops boss, whose mood worsened when Mackay's deflected shot on the hour mark sealed a miserable day for the Hoops, who hit the woodwork through Commons and substitute Paddy McCourt during an afternoon of missed chances.
"I am angry, really angry," he said. "We threw it away. We missed clear-cut chances, were complacent and wasteful in front of goal The longer the games goes on and it's nil-nil, you give the opposition encouragement."
He added: "I'm fed up with it and fed up with us missing penalties, that would have given us a real good start.
"In the final third again we were awful. It was immature. That is one way to describe it
"Paddy gets in and he has the whole goal to aim at and he hits the post and it bounces out to James Forrest and he panics and hits the defender. So there is a bit of that in our play at the minute.
"My back four gets the blame when a team scores and they don't deserve that.
"My front six were bang average and I am more angry with them than anyone else.
"We hit the post a couple of times but we missed simple chances.
"We might not have deserved the result but we got it and if you don't take your chance that's what happens in football."