Celtic 1 St Mirren 2
Callum McGregor called for lessons to be learned after Celtic's demoralising 2-1 home defeat to St Mirren on Saturday.
After a 2-0 victory over Hamilton Academical at Parkhead in midweek gave the reigning champions their first win in five, Neil Lennon's side took a backward step against the Buddies.
Kristian Dennis gave the visitors the lead in the 18th minute with a well-worked goal and although French striker Odsonne Edouard levelled just after the half-hour mark, Jim Goodwin's side refused to buckle.
Some curious defending by Celtic defender Shane Duffy allowed Ilkay Durmus to fire in what turned out to be the winner in the 37th minute to give the Paisley side their first victory in the east end of Glasgow since April 1990.
Lennon described the afternoon as the lowest point of his two spells as Celtic boss and the Hoops' quest for 10 successive Scottish Premiership titles looks over as Old Firm rivals Rangers remain 23 points clear having played two games more.
Scotland midfielder McGregor, captain again in the absence of Scott Brown, said: "It was really poor again. We are not learning lessons that we have to.
"Granted it is a new, younger feel about the squad, but there is no doubt we are in transition in terms of being able to consistently perform.
"We have bits in games where we look alright and then we go to sleep, we don't do the basics.
"You see the goal, it is just organisation and the second one is the same, we miss the first tackle and then we are all over the place.
"We have so much learning to do and the only way to do that is to keep working and try to stay positive in terms of learning, but at the same time we have to get results and we are not doing it so it is not good enough."
McGregor said the midweek performance was "excellent" but because of a number of young players in the side "consistency is going to dip".
He said: "You see our team now, it is fairly young and we have to learn and that is going Wednesday - Saturday - Wednesday - Saturday all the time.
"The boys will get there, but that is where we are at, at the minute."
Saints boss Jim Goodwin hopes his side get the credit for their historic win.
He said: "I don't think it was a case of Celtic not being at it. I wouldn't say they weren't trying.
"You could see they were desperate to get on the ball and make things happen.
"My players deserve all the credit. Sometimes it's all about how bad Celtic or Rangers are after these results and the opposition don't get the credit they deserve."