Neil Lennon felt a 1-0 defeat at Ross County encapsulated Celtic's season.
Lennon claimed they had played better than they had at Dingwall in September when they won 5-0.
But he was left frustrated at their failure to take their chances with Ryan Christie the biggest culprit, missing a series of opportunities which included him blazing over the top of the stand from seven yards.
Jordan White was then allowed to head home unchallenged from Harry Paton's 71st-minute free-kick to consign Celtic to a second defeat by County this season.
The result leaves them 18 points behind Rangers with eight games left and heightens the prospect of the leaders clinching the title at Celtic Park on March 21.
"It's a strange one, it's a game we should have won out of sight," Lennon said.
"I think it encapsulates the season really. We have dominated the game, dominated the chances – and they weren't half-chances, they were gilt-edged – and then we have conceded another set-play, which has been a real weakness for us this season. Really, really poor. And the build-up to the free-kick has been poor as well.
"But we came here and won 5-0 and didn't play half as well as we did tonight. That's football sometimes."
Celtic conceded a set-piece goal in their Betfred Cup defeat by County and Lennon is frustrated at their inability to deal with balls into their box.
"I can't do it for them," he said. "It wasn't a problem for us last season but it's been a real problem this season with more or less the same personnel.
"You have got to want to go and head the ball, block runners. I don't see us getting any free headers in the opposition box but I have seen that plenty of times for us and it's not been good enough.
"We were zonal and (Diego) Laxalt has got a job to do on the block but it's just too easy. (Kristoffer) Ajer's there, (Scott) Brown's there, we have enough players to deal with it, and we haven't. It's not good enough.
"The ball has been in our box one or two times in the second half and we concede. There's a softness about us this season.
"We shouldn't be losing to the bottom team. We shouldn't be losing the manner of goal we lost again."
County climbed above Hamilton and Kilmarnock and out of the relegation zone.
Manager John Hughes said: "I am absolutely chuffed to bits with the result. Credit to the boys their effort and commitment, their organisation, their willingness to put their body on the line.
"It's Glasgow Celtic we are playing against, there had to be an understanding that we couldn't be wide open.
"Tactically we were spot on and to go and score the goal, something we have been banging the drum about, all about delivery, and the delivery from Harry Paton and Jordan (White) peeling round the back, absolutely delighted.
"I thought big Jordan was different class and led the line really well."
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