An under-strength Chichester suffered a blow at Thurrock as they slipped to a 20-12 defeat in London One South.
Last minute withdrawals meant they made the trip to Essex with only two replacements.
Blues made five changes to the side that hung on for the victory against Dartfordians as Dane Gingell, Tyrese Makasi and John Lindsay joined the forwards, Shaun Baker returned in the backs and Tom Bowman was on the bench.
Chichester, with a gusting wind off the Thames Estuary behind them, found themselves pinned into their own half from the start but looked comfortable and soaked up the pressure.
Thurrock got the first score of the match with a 35-metre 15th-minute penalty and added a second two minutes later as Chi infringed again.
It took Blues 21 minutes to cross the halfway line with the ball.
A series of phases got Chi to within 12 metres of the try line but the ball was spilled to allow Thurrock to clear their lines.
A five minute period of pressure from Blues nearly resulted in a try from Tom Blewitt but he was tackled into touch just short by the Thurrock full-back.
Shortly after, Blewitt landed a penalty from in front of the posts but Thurrock moved further ahead with a well-worked move that finished with a try out wide and a fine conversion for a 13-3 lead.
In the final minutes of the half Blewitt kicked two further penalties to reduce the deficit to 13-9 and half time.
The second half started like the first, with Blues pinned in their own half.
With 48 minutes played, Thurrock’s fly half sliced through as they added a converted try.
Blewitt reduced the deficit off the tee on 63 minutes but Blues could not find the offload to release a runner and unlock the Thurrock defence to add another crucial try.
Blues left Essex frustrated that they did not take their chances and secure a losing bonus point.
Man of the match was Tom Bowman, who had expected to be on the bench for the 2nd XV.
Chichester’s next match is on Saturday, December 7, when they entertain Camberley. Bognor let Fareham Heathens off the hook as they lost 17-14 at home in the Hampshire Premier.
Skipper Josh Burgess said: We bossed most of the game and then let them get some cheap tries off our mistakes.”
Jeremy Newton and Chris Hay got the Bognor tries.