Portsmouth paid the price for not taking their chances in their 40-7 defeat at London three south west leaders Winchester.
Head coach Neil McRoberts felt it was a brutal lesson for his promotion-chasing side.
They felt confident at the break they could turn the bad weather in their favour.
It was set up for a push from the team in the second half.
But they just couldn’t get the points they needed when they were on top.
McRoberts said: ‘The margin of defeat didn't reflect the game.
‘Winchester gave us a lesson in being clinical.
‘If you don't take your chances against the top sides then you are going to get punished.
‘When we were only 19-7 down at half-time after playing against the elements it looked good.
‘We camped in their twenty-two for the opening 15 minutes of the second period.
‘When you do that it is vital that you make it count and come away with points.
‘For some reason though we stopped playing our structures and started to do silly things.
‘We attempted 50-50 downloads and kicked ball away.
‘Winchester did the exact opposite and converted even the slightest of half-chances.’
The Portsmouth score came from winger Luke Simmons who intercepted a pass and raced in for half-way.
Simon Morgan added the conversion.
Elsewhere in London three south west United Services Portsmouth lost ground with a 17-6 defeat at Battersea Ironsides.
Petersfield improved their survival chances with a 17-14 home win against Warlingham.