With the last pair at the wicket, Warwickshire needed 12 off the last over and six off the last two balls when Small launched into Malcolm, sending the ball soaring past the helpless Derbyshire captain Dean Jones, who lost sight of the ball in the early evening sunshine at Derby.
Small had earlier played a big part in restricting Derbyshire to 216 for 8 by claiming 3 for 41. Derbyshire's innings began in explosive fashion with Chris Adams strengthening his claims for a call into England's one- day squad with a flamboyant 61.
Adams hit 11 fours and a huge six off 61 balls in a thrilling 114-run opening partnership with Kim Barnett which threatened to set Warwickshire a daunting total after they won the toss and decided to field. But Small dismissed Adams, Dean Jones and Gul Khan in a superb spell to spark a Derbyshire collapse as they lost eight wickets for 87 runs.
Warwickshire, who needed victory to qualify on a higher run-rate than their opponents, had looked comfortably on course after Nick Knight, who made 69 in only his second innings since breaking his finger in New Zealand, and Dougie Brown steered them to within 83 runs of victory with nine wickets in hand and 19 overs remaining.
But an astonishing collapse with eight wickets falling for 69 in 17 overs, after Vince Clarke dismissed Brown, David Hemp, Dominic Ostler and Knight in quick succession, established Derbyshire as favourites before Small's late flurry.
A rained-off match maintained Kent's unbeaten run in the qualifiers to give them a home tie in today's draw. They took a point from an abandoned game at Bristol which saw them make 239 for 7 and Gloucestershire replying with 50 for 1.
The tie between Scotland and Nottinghamshire was abandoned without a ball being bowled following an 8.30am inspection at Edinburgh. The two sides, who occupy the bottom two places of Group B, were awarded a point each, as were Ireland and Essex whose game in Downpatrick was abandoned.Reuse content