Williamson is not part of the Yorkshire side taking on Surrey in the County Championship at The Oval from today as he is, in the words of the Yorkshire management, feeling “mentally fatigued”.
A glance at the schedule shows that Williamson, the 25-year-old New Zealand captain, has been playing pretty much non-stop for several months.
Prior to his return to Yorkshire last month, he was on duty in the Indian Premier League and, before that, he was playing for his country in the World T20.
But, mentally drained or otherwise, Williamson, shortly to be replaced by Australian batsman Travis Head, overcame such problems yesterday to make his highest T20 score for the club.
His innings of 65 eclipsed his previous best of 48, which had come less than 48 hours earlier in the two-run win over Birmingham Bears at Headingley, and underpinned a Yorkshire score of 166-6 after they had been sent into bat.
Adil Rashid then took 3-20 from four overs as Derbyshire – just like Birmingham Bears on Friday night – imploded at the end of their run-chase.
Needing 25 from the last three overs with six wickets in hand, they came up one run short at 165-8, Yorkshire’s third successive win sending them fifth in the North Group and putting them back on course for the quarter-finals.
Williamson came to the crease in the sixth over after Yorkshire lost Adam Lyth and Alex Lees.
Lyth looked in good touch as he pulled Shiv Thakor for four and then eased him to the cover boundary before upper-cutting Matt Critchley into the hands of third-man.
Lees fell for a duck when he drove at Thakor and was caught behind, but David Willey injected impetus on his way to 33 from 28 balls, including successive leg-side sixes off James Neesham.
Williamson was third out at 80 in the 11th over, driving off-spinner Wes Durston to Wayne Madsen running in from long-off.
Jack Leaning managed only a single before falling lbw to Critchley, and Yorkshire slipped to 101-5 in the 15th when the Durston/Madsen combination accounted for Will Rhodes to another catch in the deep.
But Williamson, who freed himself up by launching Andy Hughes for a straight six, kept the scoreboard ticking with a classy exhibition of power and placement.
He went to fifty from 38 balls with five fours and a six, and he struck a second maximum when he thumped Thakor over the top.
Williamson played a delightful shot when he spanked fellow countryman Neesham for four down the ground, but he fell to Neesham’s next delivery when he was bowled making room in an effort to hit to leg, ending a stand of 48 from 27 balls with Tim Bresnan.
Bresnan hit the last ball of the innings for six over cow-corner off Andy Carter on his way to an unbeaten 24 from 14 balls, Liam Plunkett ending undefeated on nine.
A heavy shower during the interval between innings sent spectators scurrying for cover, but it was not long enough to take time out of the match.
When the action resumed, Durston fell to the 10th ball of the reply, lbw to Bresnan, but Hamish Rutherford got the hosts going by striking Willey for six over extra cover and propelling his next delivery through the same region for four.
Rutherford added 73 for the third-wicket from 49 balls with fellow countryman Neil Broom as Yorkshire struggled to gain control. But Rutherford perished for 44 when he overbalanced to leg-spinner Rashid and was stumped, Rashid striking again to have Broom lbw for 37 as Derbyshire slipped to 102-3 in the 14tth over.
Rashid claimed his third wicket when Madsen was another stumping victim, but Yorkshire encountered a frustrating obstacle in the form of Chesney Hughes, who clubbed Bresnan for two sixes in an over – one of which sailed out of the ground over long-on.
But Hughes gave it away when he skied Willey to Bresnan at cover, and the England left-armer struck again when Neesham pulled flatly and firmly to deep mid-wicket, where Plunkett plucked out a brilliant catch just above his head.
Andy Hughes holed out to deep mid-wicket and Thakor was run-out, and although Critchley hit the last ball of the match for six over mid-wicket off Rafiq, it was not enough to overhaul the visitors’ total.