Northamptonshire 153 for 2 (Willey 47*, Vasconcelos 42) beat Gloucestershire 152 (Charlesworth 68, Sanderson 4-20) by eight wickets
David Willey played a captain's knock of 47 not out to steer Northamptonshire Steelbacks to a Vitality Blast quarter-final win as they overcame Gloucestershire by eight wickets at the cinch County Ground, Northampton.
Willey picked up the mantle after Chris Lynn was forced to leave the field when Duan Jansen struck him on the foot and Ricardo Vasconcelos was dismissed for 42.
The win books Northamptonshire a place at Vitality Blast Finals Day for the second year running.
For Gloucestershire, Ben Charlesworth played a lone hand with a brilliant career-best T20 score of 68 off 38 balls. But only Jack Taylor (24) contributed any other significant score and with wickets tumbling regularly, the visitors were bowled out for 152.
Ben Sanderson claimed his season-best figures of 4 for 20 with leg-spinner Calvin Harrison taking 2 for 23.
The Steelbacks struck twice in the opening two overs. First the dangerous Dawid Malan pulled Willey to backward square before Sanderson snared Graeme van Buuren, caught at mid-on.
D'Arcy Short though started to find his groove, twice driving Willey to the extra cover boundary and smashing Sanderson down the ground. But the veteran seamer had the final word, castling Short to leave the visitors on 16 for three.
Runs started to flow as Charlesworth smashed 22 off Willey's third over. He made the most of a quick, dry outfield, driving crisply and pulled the Steelbacks skipper for six out of the ground. He swung George Scrimshaw for two huge sixes too.
Charlesworth reached his half-century and brought up Gloucestershire' 100 off successive balls, but James Sales struck later in the over to account for Jack Taylor. The Gloucestershire skipper, who had largely played the anchor role, attempted to pull and gloved behind.
Gloucestershire then lost two wickets in six balls. First Kamran Dhariwal was brilliantly run out by Ricardo Vasconcelos and Harrison, then Miles Hammond made room to play Scrimshaw and was bowled.
Charlesworth finally fell, coming down the wicket to Harrison and edging to backward point, before Duan Jansen was trapped lbw next ball.
Sanderson then returned to bowl Matt Taylor and Marchant de Lange in the final over.
Lynn uppercut Matt Taylor over point, crunched through cover and dispatched him over cover. Vasconcelos, meanwhile, cut the seamers to good effect, behind and in front of square.
When Lynn was forced off at the start of the seventh over, Nathan McSweeney took the baton, swotting Short through mid-off and driving de Lange through midwicket. The Gloucestershire bowler made the first breakthrough though when Vasconcelos chipped to mid-off.
McSweeney and Willey played low-risk cricket, running ones and twos hard to keep wickets in hand. No boundaries came in 24 balls after Vasconcelos' wicket, but the pair kept the scoreboard ticking. McSweeney finally broke the shackles, pulling past a diving Short at deep backward square.
Short finally broke the partnership when McSweeney was lbw attempting to sweep. Willey though smashed Matt Taylor through cover and Lewis McManus took on the pace of de Lange, pulling for four and six.
Willey smashed Jansen down the ground for six with victory arriving next ball.
