Guernsey FC coach Colin Fallaize says his side's good start was partly to blame for their 5-1 loss at Whyteleafe.
Matt Loaring gave Guernsey a 19th-minute lead, but two goals five minutes before half-time and three more after the break killed off the islanders.
"We started so well and were in control, but from that 20-minute period we didn't take the game forward," Fallaize told BBC Radio Guernsey.
"We showed a bit of naivety and lack of understanding of what we need to do."
The loss means Guernsey FC have still not won an away game since December 2015 and have dropped to 19th in the Isthmian League Division One South.
"Football-wise I'm expecting a little bit more from us in terms of the maturity that we should be gaining from five or six years playing at an improved level than what we get on the island," added Fallaize.
"I would strongly suggest that they look at the full 90 minutes and take a full evaluation of the opportunity that they provided for themselves in that first 20 minutes.
"If they look at it in a learning way and see that they missed opportunities to take their game forward and take Guernsey FC forward with at least a point."