Guernsey FC were "not really quite good enough" in their 4-1 Isthmian League Division One South defeat at Chipstead, says first-team coach Colin Fallaize.
Guernsey played for around an hour with 10 men after Angus Mackay was shown a straight red card for a challenge.
"I've seen a lot of changing rooms and that's not a comfortable one at the moment," Fallaize told BBC Guernsey.
"You certainly learn the hard way and we were punished for some moments of poor decisions and technical ability."
Glyn Dyer scored for the Green Lions but it proved to be no more than a consolation, while Mike McGrath was injured in the warm-up with suspected concussion.
"It was a day that's not really quite good enough," added Fallaize.
"Of course anybody that pays their money to come through the gate, I've got no problem about them venting their opinions but it certainly hurts the boys.
"We all as a group, as coaches, as players have to take full responsibility for what I think was a job not done well enough."