Norwich City U21s suffered late heartbreak in the opening game of their Premier League Cup campaign against Exeter.
The Canaries trailed for an extended period in the second half after Jonathan Tomkinson's own goal minutes after the interval but thought they'd found a late equaliser when Finley Welch swept debutant Brandon Forbes' cutback into the far corner.
But Theo Cutler's strike in stoppage time condemned category one Norwich to a defeat against the category three League One outfit.
City's deadline day additions Forbes, Billy Gee and AJ Bridge were all named amongst the substitutes, whilst Tomkinson, who was unable to find a new club during the summer window, captained the Canaries at St James Park.
Exeter nearly snatched an early advantage when Jay Bird, a first-teamer returning from injury, directed a shot off-target inside the opening two minutes.
The first opportunity of the encounter for Norwich fell to Errol Mundle-Smith in the box, but his drive was saved well by Exeter goalkeeper Harry Lee, who strongly palmed his effort away from goal.
A slick counter attack for City in the 28th minute saw striker Dan Ogwuru burst up the pitch before laying Welch in behind. He checked inside the defender before lifting a shot over Lee's crossbar.
Exeter came close to opening the scoring after Amani Richards' shot ricocheted off the impressive Caleb Ansen and bounced into the path of substitute Cutler, but he was unable to make solid contact with the ball, allowing the City keeper to catch it fortuitously.
City emerged after half time with more intensity but found themselves behind inside the opening seven minutes when Tomkinson diverted Richards' cross past Ansen and into the net to hand the League One side the lead.
Exeter were close to doubling their advantage four minutes later when Pedro Borges connected with Mitch Beardmore's cross, only for Ansen to again come to Norwich's rescue by somehow pushing the effort onto the post to keep Neilson's men in the contest.
City made a quadruple substitution on 62 minutes as Neilson sought a reaction to going behind with all of City's new recruits thrown into action. That nearly yielded an instant response when Mundle-Smith connected with Welch's low cross but could only direct the shot straight at Lee.
With City chasing an equaliser at one end, Exeter went close to adding a second in the 72nd minute when a ball across goal fell for Cutler, who somehow swept his effort wide of Ansen's post.
Welch had an opportunity to equalise with five minutes left on the clock after Forbes' cutback from the right, but the legs of Lee saved his effort.
That combination was then at the heart of City's equaliser a few minutes before the full-time whistle. Forbes' cross from the right found the on-running Welch who, at the second attempt, found the bottom corner expertly to restore parity.
Just two minutes later, Exeter restored their lead in dramatic fashion after great work from Caleb Watts before finding Cutler, who weaved past two City defenders before lifting the ball into the net past Ansen in stoppage time to secure the victory.
Norwich's next fixture in this competition will pit them against Bristol City at Colney in October.
Exeter City U21s (3-5-2): Lee; Cummins, James (C), Cayliss; Oakes, J Richards (Cartwright, 87), Borges (Crees, 87), Dean, Beardmore; Bird (Cutler, 25), A Richards (Watts, 66). Subs not used: Phillips (GK)
Goals: Tomkinson (o.g) 52, Cutler 90+1
Bookings: James 90+2, Oates 90+5
Norwich City U21 (4-3-3): Ansen; Okwumo (Doy, 63), Tomkinson (C), Wilson, Mahovo; Bracking (Bridge, 63), Djedje, Welch; Roberts (Gee, 63), Mundle-Smith; Ogwuru (Forbes, 63). Subs not used: Finch (GK)
Goal: Welch 88
Bookings: Welch 90+4
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