It was an uncharacteristic individual error from Pompey’s keeper that saw them fall behind for a second time at Rotherham.
The keeper spilled Ollie Rathbone’s shot to allow Michael Smith to score for the home side after his earlier goal had been cancelled out by Marcus Harness.
But it is what happened next that angered Danny Cowley, who watched his troops concede twice more in quick succession to suffer a 4-1 defeat.
And he knows his side have to defend a lot better if they are to arrest a run of form that has seen just one victory secured from the past 11 games.
The Blues boss said: “For 55 minutes I thought we had a really good place in the game and it’s ended up being a disappointing day for us.
“We were unlucky to go in 1-0 down at the break because we had played with a good rhythm and were in control.
“There were five or six moments when we got into dangerous areas and were just missing that execution.
"You can’t concede three times in seven minutes – you just can’t. We have to look at that and learn from it to try to get better."
“But we gave away too many crosses and knew that would be a threat because of Smith peeling away. We weren’t able to stop that.
“Our response was good and we came out a better team after the break. We scored and you thought we would really push on.
“Then we conceded a bad goal. Gavin has been excellent up to this point and he made a mistake, which happens.
“But our response from that was well short – the durability and substance you need in those difficult moments wasn’t there.
“You can’t concede three times in seven minutes – you just can’t. We have to look at that and learn from it to try to get better.
“We need qualities like grit and determination from within. We’re not very good when things go against us at the moment – we can’t find the answers.
“Rotherham didn’t have loads of chances and we didn’t defend well enough. Credit to them because they showed us what 'good' looks like in League One.
“We just went under and it’s hard for me to say, but I’m the one who has to take responsibility for that.”