Stromsgodset, a team of part-timers from the fishing port of Drammen, had snatched two goals midway through the first half and were within 10 minutes of a stunning victory when the 17-year-old Vassell was summoned from the bench. Within two minutes, Gary Charles's goal gave Villa hope against a side depleted by the dismissal of their captain, Kenneth Karlsen, for a second bookable offence.
Only 12 seconds remained when Vassell sidefooted the equaliser. Three and a half minutes into stoppage time, the England Under-18 striker pounced again to complete an extraordinary fightback.
Villa, quarter-finalists last spring, surely did not envisage an evening of such high drama. While they lead the Premiership, Stromsgodset lie ninth in their domestic league with Norway's worst defensive record.
Perhaps the visitors' poor pedigree - they lost 11-0 at Anfield in 1974 - had induced complacency in the Villa ranks. After all, John Gregory, their manager, had stressed that the league took priority over Europe.
Whatever the truth, Villa were 2-0 down after only 23 minutes. Injury- hit Stromsgodset used a wing-back, Anders Michelsen, as a lone striker. The ploy reaped a rich dividend in the 21st minute after he muscled his way past Gareth Southgate. Michelsen's right-foot drive was beaten out by Mark Bosnich, but rolled obligingly for him to stroke in the rebound.
Villa were still coming to terms with being behind for the first time this season when the Norwegians doubled their advantage. Christer George, who had replaced Hans Erik Odegaard following an over-zealous challenge by Alan Thompson, steered the ball wide of Bosnich after Rune Hagen's cut-back.
Villa stepped up the pressure in the second half, opening up the flanks and troubling Glenn Arne Hansen. Darren Byfield, another young prospect, had the two best chances to halve the deficit, although Bosnich prevented Michelsen putting the outcome beyond doubt in a rare counter-attack.
Despite Karlsen's dismissal for fouling the substitute Riccardo Scimeca, Villa appeared destined not to find a way through a massed defence. Thompson, however, maintained his prolific service; following one of his crosses, Charles gave Villa a lifeline with a scrambled goal.
Another centre, by Alan Wright was headed back across goal by Scimeca and miscued by Lee Hendrie, whereupon Vassell hauled Villa level in front of a delirious Holte End. When Hansen could only parry Thompson's drive at the death, their new hero followed in to seal a success which had looked highly implausible only minutes earlier.
"Darius is a local boy who has come through the system at the club," Gregory said afterwards. He lives only a mile from our training ground and has been a prolific scorer in our junior teams. I have never felt able to trust him for 90 minutes before but tonight I took a shot in the dark and he got us out of jail."
Aston Villa (3-5-2): Bosnich; Grayson (Taylor, 37), Southgate, Barry; Charles, Hendrie, Draper (Scimeca, 67), Thompson, Wright; Joachim, Byfield (Vassell, 80). Subsitutes not used: Ferraresi, Hughes, Jaszczun, Oakes (gk).
Stromsgodset (4-5-1): Hansen; Granas, Karlsen, Waehler, Skistad; Nyan, H Odegaard (George, 10; Strom, 71), Solberg, Kihle, Hagen; Michelsen (Olsen, 88). Subsitutes not used: Horsrud, Johnsen, Sannerholt, T Odegaard (gk).
Referee: H Strampe (Germany).Reuse content