Portsmouth slipped back into the bottom three of London one south after a disappointing 47-24 defeat at Cobham.
With four games remaining the city club face a huge battle to avoid relegation.
Coach Ian Chandler knows his young side have to learn their lessons quickly if they are to survive.
‘I am a bit deflated,’ said Chandler.
‘Cobham played a good, expansive game but we paid for our naivety yet again.
‘We dominated the opening 20 minutes of each half but failed to make it count.
‘All we had to show after the first 20 minutes was three Andy Barnes penalties and then one big missed tackle let them in.
‘That gave them the encouragement they needed and by half-time they had rattled up 26 points.
‘That’s when the game was lost.’
Adam Long scored a catch-and-drive try at the start of the second half to put Portsmouth back in it.
But crucially Cobham broke out to score again.
‘If we don’t learn quickly then we could lose our place in this league,’ said Chandler.
‘Three of our last four games are at home and if we win those we will be safe.
In Hampshire one, United Services closed the gap on second-placed Fordingbridge to four points with a 23-12 win over Ventnor.
Southsea Nomads suffered a 31-10 home defeat by Romsey.
Petersfield recorded an excellent 13-11 success over Millbrook at Penns Place.
In Hampshire two, Fareham Heathens had to settle for an 8-8 draw at Lymington Mariners.