With skipper Ian Westwood out for six weeks with cracked fingers tips, Warwicks named Coventry born Luke Parker and Ant Botha as skipper who promptly lost the toss.
Somerset Sabres batted first with Justin Langer and former England international Marcus Trescothick opening the batting. At the end of the third over in which Trescothwick hit two straight sixes, Somerset who have won their last three matches were 31-0.
The first wicket fell with the score on 68 when Langer came racing out to hook the ball but was yorked by Tim Gronevald. Two balls later, Gronevald removed Trescothwick.
Warwicks, still needing at least one victory to win the group and get a home tie in the Quarter-Finals, had turned the screw and in his second over, Gronevald took his third wicket of the day when he removed Blackwell for one with the score on 75-3 and then Trego gave Salsibury an easy catch just before the halfway stage.
Zanda de bruyn was dismissed by Sailsbury in the eleventh over and two overs later, Somerset passed the 100 run mark before they lost Craig Kieswetter for 26.
The vistors kept run scoring with a couple of sixes in the final over and ended their innings on 173-6 with Banks and Suppiah both 32 not out.
Warwicks had beaten Somerset every timy they had played them but Neil Carter was out for a duck in the second ball of the innings.
Jon Trott passed the 1,000 Twenty/20 run mark and played some good shots to take Warwicks past the 50 mark in the fifth over.
In the eighth over,Warwicks were still whittling down their biggest run chase of the season. Jim Troughton made his half century off 27 balls, hitting a six to take the score to 89-1 needing seven runs an over to win.
In the next over, Troughton, Warwicks third highest Twenty/20 run maker was out for 57 to Blackwell in the 11th over, Warwicks passed the hundred mark with a six from Jon Trott who was finally dismissed for 48.
Warwicks now needed eight an over and sent in Ant Botha. Some 32 runs short, Tony Frost was out for 25 and Gronevald became the fifth Warwicks player to lose his wicket.
Luke Parker who plays his club cricket for Birmingham League side Leamington, came in to partner Botha for the final three overs.
This was getting really exciting and Warwicks needed seventeen runs from the final two overs but Parker going for a second run by de bruyn was run out for nine. After a delay to get the score right, Michael Powell took a comfortable two off his first ball then Ant Botha gave a massive boost with a six on the final ball of the 19th over.
Five balls were required in the final over. Former Warwickshire man Alfonso Thomas bowled it. Powell hit a single in ball one. Botha scrambled a run. An over throw from Juston Langer tied the match and Michael Powell hit a four to finish 14 not out and steer Warwickshire to a win by four wickets.
Remaining matches
Thursday, 26 June v Glamorgan (h) 1730
Friday, 27 June v Northamptonshire (h) 1730
Commentary on BBC Coventry & Warwickshire
Ian Bell is out of the England team for the fourth One Day international against New Zealand tomorrow after picking up a knee injury playing touch rugby!