Jack Kelly got Leicestershire off to a good start against pacesetters Yorkshire, making 44 off 31 balls, but when the New Zealander holed out off Hasan Ali it started a run of four wickets in 15 balls as they slumped from 90-2 to 96-6.
Ben Cox hit a defiant unbeaten 33, but Hasan (4-18) returned with two wickets in three balls as the Foxes were restricted to 147-8.
The total looked a meagre one when Bairstow, fresh from his 73 in Friday’s Roses clash, smashed 39 off 21 balls before becoming the first of two wickets in Ian Holland’s first over.
Will Luxton hit 38 off 27 balls to take Yorkshire to 100-3 in the 13th over, but the other Tykes batters struggled to get going as the home attack chipped away.
Aided by the farcical run-out of Moeen Ali for 11, and falling behind the rate required, the visitors lost their last seven wickets for 35 runs.
Nottinghamshire opener George Munsey set the tone at Trent Bridge with his second fifty in three matches, sharing stands of 50 with Joe Clarke and 67 with Jack Haynes, before falling for 53.
Haynes brought up his 50 off 35 balls, but went to the next delivery as Derbyshire fought back, but Tom Moores hoisted three sixes in a late cameo of 39 to lift the Outlaws to 183-6.
Pakistan pacer Mohammad Ali (3-25) continued his fine form by removing Aneurin Donald, Caleb Jewell and Matt Montgomery in the powerplay to check the Falcons’ fast start.
Most of the Derbyshire batters made starts, but Wayne Madsen’s 27 was the top score as Dillon Pennington also chipped in with three wickets to keep the visitors down to 173-9.
Lancashire failed to bounce back from their heavy loss in the Roses match on Friday as they went down to a two-wicket defeat by Glamorgan in gloomy conditions at Blackpool.
Liam Livingstone fired 81 off 37 balls, launching eight sixes in his innings, and collected impressive figures of 3-13 for the Red Rose – and with two overs remaining, Glamorgan still needed 41 to win.
Chris Cooke’s 44 not out off just 15 deliveries proved decisive though as Glamorgan chased down a target of 202 to snatch victory out of the jaws of defeat off the final ball.