Guernsey captain Blair Campbell says his side must prove that they belong in National Three London when they face second-placed Barnes on Saturday.
Guernsey were and Campbell wants an improvement.
"We let ourselves down last week," Campbell told BBC Guernsey.
"We can't win the league now, all we can do is show that we deserve to be in the league and that comes this weekend against one of the top sides."
He added: "If we can put in a performance and beat them then we can say we're worthy to be where we are."