An honest Simon Grayson said his Blackpool side showed a "lack of professionalism" as Coventry City came from two goals behind to inflict the Seasiders' first defeat of the season.
Pool produced a strong showing in the opening half but somehow found themselves going into the break on level terms.
Sullay Kaikai had struck twice to open a two-goal lead for the Seasiders, only for Coventry to be gifted a route back into the game with two quickfire responses.
Matty Godden capitalised on a defensive mix-up to reduce the arrears before Wesley Jobello equaliserd right on the stroke of half-time.
Coventry were the dominant side in the second half but left it late to grab the win, substitute Callum O'Hate netting the winner in stoppage time.
It came as Pool finished the game with 10 men after Nathan Delfouneso hobbled off injured, Grayson having already made all three changes.
But Grayson believes it was that crazy spell just before the half-time break that swung the game in Coventry's favour.
“The game turned on the final five minutes of the first half," the Pool boss said.
“We were in a strong position after getting the two-goal advantage and we were looking really secure defensively and really good going forward.
“But through a lack of professionalism to a certain degree, a lack of a reaction and a lack of doing the basics has cost us the game.
“We’re 2-0 up in a strong position but I wouldn’t have minded had Coventry played through us and got some some real good goals.
“But it’s three balls into the box which we should have dealt with, especially the first two anyway.
“There’s 6ft 3ins lads in there but we didn’t win the first ball and then we didn’t react to the second one dropping.
“It gave them a lifeline before half-time and we’re hugely disappointed to lose the game at the death.”
When asked to put his finger on why those defensive mishaps were allowed to happen, Grayson added: “There were a few factors.
“You’ve got to make sure your shape is right and you’ve also got to make sure your concentration levels are really high.
“Especially just before half time, because we didn’t have to go looking for the third goal.
“We were playing with a back three but really we should have had five there, been solid and got into half time at 2-0.
“We did it at Southend a few weeks ago where we got two goals in front and then stayed nice and solid at the back. They came looking for a goal back and we picked them off.
“Today we went looking for the third one rather than being compact and using our shape. That’s something for us to learn from.”