Derbyshire 183 for 3 (Guptill 60, Madsen 53) beat Durham 178 for 5 (Muchall 62) by five runs
New Zealand opener Martin Guptill found his form at the right time to fire Derbyshire to a five-run Friends Life t20 victory over Durham at Derby.
Guptill hit 60 off 43 balls and Wayne Madsen made his first half-century in the competition as the Falcons scored 183 for three to set up an opening win in the North Group.
Gordan Muchall led Durham's chase with 62, but after Derbyshire's spinners removed the dangerous Paul Collingwood and Ian Blackwell cheaply, the Dynamos came up short on 178 for five.
Guptill looked in good touch from the start as he dispatched the second and third balls of the innings from Graham Onions to the mid-wicket boundary.
The Durham seamers tended to pitch too short and Guptill and Wes Durston took advantage until Gareth Breese stemmed the flow with his off-spin.
But Guptill still reached his maiden 50 for Derbyshire off 35 balls before launching Ian Blackwell over mid-wicket for six.
The opening pair put on 88 in 11 overs, but when Durston tried to reverse sweep Breese he was caught behind for 25 and Guptill followed in the spinner's next over caught at extra cover off a full toss.
Chesney Hughes hit Breese over long off for the second six of the innings but Breese took a fine running catch to remove him when he pulled Onions to deep mid-wicket in the 15th over.
The Falcons were in danger of falling short until Madsen improvised well to reach 50 from only 28 balls as 53 came from the last four overs.
The South African ensured Durham faced a challenging chase but Mustard and Muchall quickly moved into overdrive despite Falcons skipper Luke Sutton rotating his bowlers.
Muchall reached his half-century off 30 balls and the pair equalled the Falcons opening stand before Mustard gave Hughes the charge with rain falling and was stumped for 36.
Hughes varied his pace intelligently to restrict the batsmen to just one boundary in his four overs and with young spinner Tom Clarke also keeping it tight, the pressure told on Blackwell who drove the teenager into the hands of long on.
Durston then landed two big blows as Muchall skied to cover and Collingwood's attempt to clear the ropes landed in the hands of deep mid-wicket.
The Dynamos needed 56 off the last four overs and despite Dale Benkenstein and David Miller plundering 18 from Durston's third over, the advantage shifted towards the Falcons when Benkenstein pulled a Steffan Jones full toss to deep mid-wicket.
Although Breese pulled Tim Groenewald for six, 15 off the final over was too much for Durham as Jones used all his experience to seal victory.