Senior coach Neil McRoberts admits their fate is no longer in their own hands.
He was left hugely disappointed on Saturday because he felt that it was a game his side could have won.
McRoberts said: ‘It was a very disappointing day.
‘Once again we failed to get ourselves up for a game when we needed to.
‘Not for the first time this season we didn’t turn up in the first half.
‘We paid the price for that in the end.
‘Playing for 10 minutes at the end of a a game is never going to be good enough.
‘Andover deserved to win it more than us.
‘We have a great group of talented rugby players in our squad but they have to learn to be focused every game.
‘Only the players can change that.’
Portsmouth started the game playing down the considerable slope but into the strong wind.
Andover drew first blood with a penalty midway through the half.
The visitors hit back quickly with the first try of the game three minutes later.
Good work by Rhys Bowen and Dan Gates enabled Jonny Stoppard to dive over for a try.
The home side regained the initiative however before Portsmouth scored again on the stroke of half-time.
Winger Noah Cannon caught a clearance kick and outstripped the home defence.
Gates levelled the scores at the start of the second half converted by Lee Chandler.
Andover again though took charge and with 15 minutes remaining had established a 29-17 lead.
Portsmouth produced a grandstand finish with further tries from Cannon and Stoppard but it proved too little too late.
Cannon collected a Chandler cross-kick to score and Stoppard crossed for his second try two minutes from the end.
McRoberts added: ‘This makes winning promotion very difficult.
‘We are now reliant on other results.
‘All we can do is go out and win every game and see where it takes us.
‘This is massively disappointing but we have to get over it.
‘As a team we need to realise that you can be as good a side as you like but you still need to do the dark work in a game.
‘Unless you do this then it will be a struggle to win games.
‘When you end up having to chase games that is when things go wrong.
‘Players become anxious, start to rush and force things with the result you lose your accuracy.’