Warwickshire 115 for 7 (Clarke 36, Willey 3-22) beat Northamptonshire 111 (Piolet 3-24) by three wickets
Fast improving Warwickshire registered their third Friends Life t20 victory in a row when beating Midlands/Wales/West group leaders Northamptonshire by three wickets at Edgbaston.
For a long time it seemed that Northamptonshire's flimsy-looking total of 111 might be too good for Warwickshire as a tense, low-scoring contest unfolded on a sluggish pitch.
David Willey put them on the back foot with wickets from the last two balls of the third over and they were seriously wobbling when William Porterfield was caught on the boundary off Steven Crook.
It took the experience of Rikki Clarke - and one bad over - to keep them in contention. Clarke targeted offspinner Matthew Spriegel for three sixes in four balls, twice clearing long-off before lining up a much bigger hit to long-on.
Although Willey came back to have Clarke caught at long on for 36, Northamptonshire had run out of seam options when Spriegel had to bowl the last two overs from the pavilion end. That proved to be decisive when Jeetan Patel, a player who thrives on spin bowling, smashed a six over midwicket with three balls to spare.
Northamptonshire's earlier struggle was largely caused Steffan Piolet, first with a brilliant piece of fielding and then with a spell of 3 for 24, a personal-best return in the competition.
The 24-year-old all-rounder ran out Cameron White with a direct hit from mid-on when the Australian was backing up at the non-striker's end. This meant Northamptonshire had lost their two overseas players from the first 15 balls. South African Richard Levi's off stump was sent spinning by Clarke's first delivery and the initial six-over power play yielded only 29 runs.
A minor recovery was under way before Piolet intervened by taking his three wickets in 10 balls. The dangerous Crook holed out to long off and in the medium pacer's last over, top scorer Kyle Coetzer fell at mid-wicket and Willey made too much room when he was bowled.
Willey targeted the shortest boundary at long on for three of the five sixes in the innings but on a difficult surface for batsmen Northants were able to hit only three fours.