In the only Eastern Premier clash to beat the rain, Leask was instrumental in his side's seven-wicket win over league leaders Aberdeenshire at Mannofield.
His four wickets first helped dismiss the Dons for a disappointing 156 before a typically robust half-century put the issue beyond doubt.
Leask was ultimately out-scored by Schalk Conradie but the Scotland and Highlanders star was the main difference between the teams.
The 23-year-old gave his side's innings the impetus it needed after they had moved somewhat laboriously to 67-2 in the 29th over.
Leask's eight boundaries underpinned a fine 55 from 33 balls. When he departed just four more runs were needed to win.
Fittingly the winning hit came from opener Conradie whose no-risk policy had been clear from the start and which reaped dividends in an unbeaten 65 from 124 deliveries.
Earlier 'Shire made the worst possible start when, having been sent in to bat, Kenny Reid was bowled by Leask in the second over.
South African-born Chris Venske opened his shoulders to get the board ticking, but, having reached 24, he became Leask's second victim, the bowler taking a safe return catch.
Only the Dons youngster Hayes van der Berg, fresh from a Scottish Cup century last weekend, achieved the necessary balance of patience and intent to stay at the crease long enough to make a meaningful contribution.
He stroked seven boundaries and cleared the rope on one occasion in reaching 55 from 85 deliveries before becoming Alistair Gill's third victim. Gill finished on 3-22 but was trumped by Leask who, having taken the first two wickets, returned to remove the last two batsmen and claim 4-30.
Elsewhere it was a tale of unremitting rain and frustration.
The torment was perhaps greatest for Carlton who were poised for a morale-boosting win against Watsonians at Myreside.
No doubt watching the storm clouds roll in from the west, the Grange Loan team raced through the 'Sonians batting line-up to dismiss them for just 98.
It was a personal triumph for former Derbyshire bowler Ali Evans, who claimed 6-19.
The good work was taken on by Fraser Watts whose hard-hitting 37 not out carried Carlton to 53-1 from eight overs.
Had a further two overs been bowled the D/L calculations would have kicked in and the win would have let Carlton leapfrog their hosts and pull away from the danger zone.
In the West, Drumpellier had reduced champions Uddingston to 54-4 before rain ended it after 22 overs.
Play lasted long enough at East Kilbride for Ayr's Scott McElnea to prove his fitness after a groin injury, sending down 10 menacing overs to claim 2-22 as the hosts reached 67-2 from 19.1 overs.
Leaders Clydesdale and bottom-of-the table West of Scotland were also beaten by the weather as their games against Dumfries and Renfrew failed to go the distance.