Jersey are no longer top of London South Two after they were beaten 14-6 at title challengers Haywards Heath.
Jersey have relinquished top spot in London South Two
Heath leapfrogged Jersey to go top by a point as both sides vie for the championship and promotion to London Division One.
Heath took the lead on 10 minutes from a converted Humphrey Baker try, before a Ben Harvey penalty made it 7-3.
But winger Simon Govett made it 14-3, before Harvey kicked a second penalty before half-time.
Jersey tried in vain to get points on the board in a scoreless second half.
Coach Barry George's men are now a point behind Hayward Heath with three games of the season left.
It isn't the end of the world, we're losing the league by one point
Jersey director of rugby
They will be ruing the deduction of two points earlier in the season for fielding an ineligible player.
Jersey director of rugby Dai Burton told BBC Radio Jersey: "They defended well, Haywards Heath, and we just couldn't break them down."
However, he was adamant the club could recover from their first loss of the season and continue to fight for promotion.
"It isn't the end of the world, we're losing the league by one point at the minute. We have the play-offs to probably look forward to, I think, now," he said.
"So there's still a chance to go up into London One. We just have to play now according to our strengths."