Brendan Rodgers attacked Celtic's second-half collapse after they were forced to rely on Arne Engels' injury-time penalty to salvage a point, and deny Dundee a famous first home win over the Parkhead side in 37 years.
He accused them of “soft” defensive errors after a certain Dark Blues team came so close to causing a major upset in a thrilling 3-3 draw.
Celtic had twice taken the lead thanks to Luke McCowan and then Yang Hyun-jun, only for Dundee to pull back twice and level thanks to a goal from Oluwaseun Adewumi and an own goal from Cameron Carter-Vickers.
Aaron Donnelly then looked set to displace Tommy Coyne as the last player to score a winning goal against Celtic at Dens Park with his 78th-minute strike, before substitute Engels converted his late penalty following a handball. Mo Sylla.
Citing Auston Trusty's failure to make a strong challenge when Donnelly headed the ball, Rodgers said: “You've got to deal with it better.” You have to stay upright, it's as simple as that.
“You're 6ft 4in, you have to deal with it better, but he knows it and he understands it.” In certain areas we weakened a little.
Engels takes an injury-time penalty for Celtic in a thrilling 3-3 draw
Aaron Donnelly scored what looked like a famous winner for Dundee after beating Trusty.
Donnelly was harassed as Dundee looked to beat Celtic at home for the first time in 37 years.
'My main concern is from a defensive perspective. Tonight it wasn't the offense (that was a problem), it was the defense.
'They are basic things. It's a game we let slip away when it wasn't necessary. Sometimes when you have mastery and you are creating, you can become a little passive.
'We don't normally do that, but we certainly did tonight. We have been very passive, especially in the second half. “The game should have been lost in the first half.”
Rodgers, whose team looked set to move 18 points clear at the top of the Premiership with victory, only to inexplicably crumble, added: “We made a great start, then lost concentration on a set piece and our organization allowed to break.”
'The youngster (Adewumi) finished well and that gave them a boost before the break. We got in front and I hope we accelerate, especially on that little slope down towards our own supporters, but we defended very poorly.
“The second goal, we have to deal with it much better and faster, then in a corner we become soft.”
“So it's not what we expected considering how well we defended and the aggression we had, but we fought until the end.” A point is not what we want but we have to take it and move on.
Rodgers congratulates Donnelly after he came so close to causing a huge upset at Dens Park.
Rodgers played down suggestions that Idah had become angry after being substituted.
Former Dundee player Luke McCowan got Celtic off to the perfect start
'You have to give all the credit to Dundee and Tony (Docherty). “We were in a good place until the goal, they fought, they were there in the second half and they deserved what they got.”
There were some suggestions that out-of-form striker Adam Idah burst straight down the tunnel after being substituted in the second half.
But Rodgers played down the incident, saying: “He went to get something warmer and then came back.”
'I give credit to the players, they kept going. But, by our standards, that second half has to be better.
Adewumi equalized with a magnificent shot for Dundee in the 41st minute.
Yang made it 2-1 against Celtic after scoring his first goal of the season.
The champions were level again when Carter Vickers' own goal made it 2-2.
“We were too passive. Too slow. On the ball, he's just not aggressive enough. “Tonight was about getting the basics of the game right and we didn’t do it well enough.”
Dundee manager Tony Docherty said he was “immensely proud” of his players but added: “The prevailing feeling is one of disappointment.” I thought we did enough to win the game.
“I saw Celtic play with (Nicolás) Kuhn, Engels, (Luis) Palma. I asked Lyall Cameron to get up from his sick bed to play, Finlay Robertson has not trained. (César) Garza has had to leave. Achieve that level of performance against that opposition borders on heroic.
“We shook a Champions League team. We sensed it, we tried and we gave everything to win that game. “I thought my players deserved it tonight.”