Crawley Town crashed out of the League Cup after losing 2-1 at home to ten-man Chelmsford.
Disappointed assistant manager Vic Bettinelli said: "You just can't legislate for the kind of individual errors which cost us two goals tonight.
"The difference between the sides was that Chelmsford took their chances and we didn't."
Reds handed teenager Scott Kirkwood his debut on the right wing.
Marc Pullan, away on England National Game XI duty, was badly missed at the back and Chelmsford profited from Reds' generosity in defence.
After just five minutes, Crawley allowed Garry Cross into the box but he pulled his shot wide.
Former Reds midfielder Keith Sharman then steered a free header wide three minutes later but the warning signs were there.
City then took the lead in the 25th minute when Danny Slatter's floated cross was steered under Andy Little by Phil Dean.
Reds almost went two down but Little denied Dale Watkins from Slatter's corner, while Ernie Cooksey went closest for Crawley with a header.
Caretaker manager Francis Vines made three changes before the hour mark, with Peter Fear, John Timlin and Warren Bagnall all entering the fray.
However, Chelmsford went two-up when Dean exchanged passes with Watkins before easily tapping in his second.
Keeper Arran Lee Barratt had to pull off a fine save to deny Danny Hockton before City were reduced to ten men.
A challenge from Cooksey left Mike Basham realing but Sharman's attack on Cooksey earned his a straight red card against his old club.
Reds pulled a goal back on 69 minutes through Ian Payne.
Crawley: Little, Holmes, Payne, Hooper, Hemsley (Fear, 45), Le Bihan (Timlin, 51), Kirkwood, Judge, McDonnell, Hockton (Bagnall, 58), Cooksey. Unused subs: Wackett, Harkin.
Chelmsford: Barratt, Statham, Clarke, Basham, Sharman, Flatter (Reid, 67), Cross, Rutherford, Dean (Samuels, 77), Watkins, Berkley (Lakin, 85). Unused subs: Street, Lay.
Attendance: 359
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