Russell Martin slammed Swansea City's lack of intensity as they were beaten 3-2 by Reading at the Swansea.com Stadium.
The Swans twice conceded shortly after scoring as they suffered what was only their second home league defeat of the campaign.
And head coach Martin felt his side were the creators of their own downfall as their eight-game unbeaten run at home in all competitions was brought to an end by the Royals.
"I'm still trying to digest it. It's nowhere near good enough," said the 35-year-old.
"Some of the stuff on the ball was great. I think maybe we fell into the trap that it was going to be really easy.
"The lack of intensity out of possession has really hurt us. Second half I thought we played some great stuff, we scored the goal and you think 'OK, maybe we'll go on to win it now' but to concede so quickly is criminal. It's such a poor goal.
"We've conceded three goals today where we've let people back inside the pitch which doesn't happen usually. That is seriously frustrating and I've told the players they should be hurt by that.
"We're really hurt to get beat. We had so many chances in the second half, the goalkeeper has made some great saves but when we're in front of the goal, people have to really give themselves up to score a goal.
"Fair play to Reading, they've got some really good players and experience, but we've gifted them three goals. It feels like we've beaten ourselves. We were nowhere where we need to be in the first 45 minutes and we've paid the price for it.
"When you play with a lack of intensity, a lack of energy, a lack of willingness to run a little bit, it can really hurt you. This group is brilliant. I told them, we love them, we love what they are producing on the pitch.
“But we need to make sure we learn from this and it doesn’t repeat itself because it’s really hurt us. We have wasted a big opportunity to make it a really great week and to really impact the league."
Tom Dele-Bashiru and Andy Carroll both struck after Jamie Paterson had given Swansea an early lead in south Wales.
And after Ryan Manning struck a stunning equaliser, Danny Drinkwater lashed home his first Reading goal to earn Veljko Paunović's men all three points.
Despite the defeat, Swansea remain in ninth place in the league table ahead of Saturday's trip to Middlesbrough.
Meanwhile, defender Brandon Cooper has signed a new contract to remain with Swansea until the summer of 2024.
The Swans also have the option to extend the Wales Under-21 international's deal by an additional 12 months.
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