We endured a frustrating afternoon as we crashed out of the FA Cup, writes James Barrett-Sterling.
Peter Adeniyi replaced the absent Tommy Bradford, while youngsters Tyrese Owen, Joel Flavien-Howard and Courtney Swaby were all named on the bench.
The game started pretty slowly and only two moments brought the crowd to life in the first 20 minutes - Levi Phillips had a shot deflected wide from 15 yards, while Chris Smith felt he was bundled over by Danny Dudley inside our area but the referee waved away the penalty calls.
The visiting striker had a glorious chance to open the scoring on 21 minutes as Rob O'Toole picked him out with a cross from the right, but Smith guided a free header over from close range.
Jordan Cheadle came forward on 26 minutes and he came onto a pass, cut inside an opponent and unleashed a shot from 30 yards - sadly it flew just wide of the far post.
We lost Ola Sogbanmu, following a 50/50 challenge with O'Toole that seemingly jarred something in his leg, and so Flavien-Howard was introduced for his first-team debut.
We had a chance just before the end of the half as Mike Dixon stole onto a loose ball and squared it to top scorer Ricky Korboa, but his eventual strike from 20 yards rose just over the crossbar.
HALF-TIME: 0 - 0
We started the second-half brightly with Flavien-Howard hitting a pot shot into Josh Pelling's midriff, and the youngster had another go on 52 minutes but his effort just flew wide of the far post.
But Horsham had chances too - Shelley put a free header on a delivery from the left over, while Smith hit a 20 yard free kick straight at Billy Bishop.
Jacob Mendy was introduced for Phillips just after the hour and the winger's first real involvement eventually saw him smash a cross-shot across Pelling's six yard area.
Then Dixon did well to spin on a pass into feet and fire an early shot off inside the visitor's area, but Pelling stood firm and blocked the ball away.
But it was Cheadle who came closest to breaking the deadlock on 78 minutes - he joined in an attack and, after the ball had been cleared back towards him on the near touchline, he thumped a diagonal ball in that was going to dip inside the top far corner until Pelling dove at the last second and tipped it away for a corner.
That delivery was cleared but Adeniyi and then Korboa kept the ball alive, only for Dixon to eventually divert it onto the roof of Horsham's net.
Bishop was alive to a dangerous through ball a minute later and bravely claimed it in front of a charging Smith.
And it seemed like the game was destined to end goalless until we gave away another needless free kick 20 yards from our goal and Charlie Harris stepped up to bend the ball inside the near post.
We had one final chance in added time as we put a free kick into Horsham's area. The ball was half-cleared but Morath-Gibbs knocked it back into the danger zone. It eventually fell to Dixon who, from only six yards out, swiveled but failed to connect with his shooting foot.
We host Leatherhead on Monday 27th August before travelling to AFC Hornchurch on Saturday 1st September.
Carshalton Athletic: Bishop; Morath-Gibbs, Dudley, Hamilton-Downes (c), Cheadle; Adeniyi, Aziaya, Sogbanmu (Flavien-Howard - 38); L Phillips (Mendy - 62), Dixon, Korboa
Unused subs: Price, Dos Santos, Owen, Swaby
Horsham: Pelling, Metcalf (c), McElligott, Harris, Shelley, Lovegrove, Hoare (Richard-Brown - 74), Hayward, O'Toole, Smith (Boswell - 89), Harding
Unused subs: Farmer, Hyde, Landais, Hartley, Punter
Goal: Harris (86)
Our 'Man of the Match': Michael Aziaya