Jordan Reynolds says the island's lack of rugby resources is impeding Guernsey RFC's ability to make greater strides.
Player-coach Reynolds spoke after Guernsey suffered an eight-try, 57-5 loss to Tonbridge Juddians in National Three London South East on Saturday.
He said: "There seems to be a big void between where we are and where a lot of the rugby on the island is, and that's causing a lot of issues.
"We just don't have the depth," Reynolds added.
"We suffer injuries and we have to make selections, and some players aren't capable of stepping up to National Three."
But Reynolds, whose side is in National Three following back-to-back promotions, was at pains not to make excuses for his team's performance on Saturday, saying they had got what they deserved.
"Tonbridge were by far the better team. We weren't on the money at all. The result probably reflects exactly how the game went.
"We're not hiding from anything. We definitely failed to produce any good rugby on the day and I blame myself a little bit for that as a coach and I think the players blame themselves a little bit as well.
"We have taken a real hit and we need to regroup. There are no excuses for what happened.
"When you are not on your game and you don't have the mental attitude, you go from losing a game to being beaten by a lot.
"There was a mental lapse that let us down."