After a bright first half performance the Robins fell away badly in the second and ultimately paid the price for their consistent inability to pose a goal threat, a problem that looks no nearer being solved judging by this display against a Chelmsford team running into form after an indifferent start to the season.
The start of the game was delayed due to City's late arrival and the first meaningful action occurred after two minutes when the City trainer deservedly received his marching orders for calling the linesmen a cheat.
Carshalton pushed Marshall into an advanced position in Omari Coleman's absence and his pace and persistence kept the City defence on their toes.
Things were looking good after 20 minutes when Marshall chased a long pass to keep the ball in play before cutting the ball back to Dundas.
The Robins striker's shot was stopped by one of several defenders around him, but the referee spotted a handball by a City player and pointed to the spot.
Carshalton captain John Cartledge accepted responsibility and became the latest penalty taker but his effort lacked power and goalkeeper Richard McKinney saved comfortably.
Carshalton seemed to weather this latest setback and continued to give as good as they got.
City looked dangerous at set-pieces, but Toppin was competing well in the midfield for the home team and Matt Howard was inches away from getting on the end of a long cross by Jabbie. Half-time arrived with everything to play for.
The second period turned out to be a major disappointment for the Robins and their supporters.
The enthusiasm of the first half was replaced by uncertainty and on 50 minutes City took the lead. Ricky Holmes was able to break away down the right and held off Harwood's challenge to poke the ball past Paul Seuke.
A soft second 10 minutes later left Carshalton looking defeat in the face when a free-kick taken by Mark Noto just outside the area found its way past a poorly positioned defensive wall and goalkeeper to creep in just inside the upright.
A series of stoppages due to infringements on and off the ball destroyed any chance of Carshalton getting back into the game and City's Kezie Ibie experienced the highs and lows of the game by picking up a poor clearance and waltzing round several defenders before knocking in the third goal seconds before being booked for a senseless foul on Harwood.
By this time, however, City were playing without any pressure and at the final whistle a dejected Robins team were left wondering what the outcome might have been if they had taken the lead from what turned out to be their one clear cut chance of the evening.
Robins: Seuke, Hartburn, Graves, Cartledge, Harwood, Howard (Fontana), Toppin, Drewett (L Coleman), Jabbie, Dundas, Marshall.
Subs not used; Platel.
Next games - Saturday 21 October Carshalton Athletic v Potters Bar Town FA Trophy - 1st Qualifying Round Saturday 28 October Staines Town v Carshalton Athletic Ryman Premier Division
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