Royal London One-Day Cup champions Nottinghamshire reaffirmed their credentials with a thrilling come-from-behind nine-run win over Lancashire at Old Trafford.
On the competition's opening night, the Outlaws defended a target of 319 as Lancashire slipped from 245 for three after 40 overs when it looked like they would secure their record chase.
Former Lancashire batsman Steven Mullaney (70), Ross Taylor (58) and Chris Nash (52) all made important contributions as Nottinghamshire reached 318 all out from 49.5 overs.
While the last 10 overs yielded 106 runs, Lancashire leg-spinner Matt Parkinson claimed all of his five wickets inside the last seven on the way to career best figures of five for 68 on his Red Rose list A debut.
Lancashire's Keaton Jennings hit a brilliant 136 from 129 balls but, despite a third successive century in all forms, he fell in the 47th over to leave the score at 288 for six.
Harry Gurney had him caught at square-leg pulling before Jake Ball struck twice in the next over.
Left-arm seamer Gurney finished with three for 61 as Lancashire, who saw Dane Vilas and captain Liam Livingstone make 41 and 33, fell agonisingly short on 309 for nine.
Tom Westley gave a reminder of his ability to the England selectors in Essex's six-wicket win over Middlesex at Radlett.
Westley, who won five Test caps last summer before being omitted for the winter Down Under, has struggled for form in the Specsavers County Championship this season.
But he hit 134 and shared a second-wicket partnership of 153 with Varun Chopra as last year's semi-finalists cruised home with 7.2 overs to spare.
Middlesex made 250 from 48.3 overs, with Nick Gubbins (50) top scoring and Ravi Bopara (three for 30) and Neil Wagner (three for 40) making the major in-roads with the ball.
Essex were always in command as Westley and Chopra (59) got on top of the Middlesex bowling, and Dan Lawrence (35) ensured there would be no late scares for the visitors.
Sussex were also comfortable Group B winners with a seven-wicket victory over Kent at Hove.
Luke Wells produced a man-of-the-match show as his leg-spin helped dismiss Kent for 188, opener Daniel Bell-Drummond the last out for 90 from 115 balls.
Wells took two for 30 and then anchored Sussex's response with 62 from 89 balls.
Skipper Ben Brown made an unbeaten 73 as Sussex coasted home with 10.1 overs to spare, only their fifth win in the competition since 2015.
Derbyshire proved too strong for Group A rivals Warwickshire with a 57-run victory at Edgbaston.
Skipper Billy Godleman led the way with a career-best 137 from 116 balls as Derbyshire piled on 357 for eight, their highest list A total against a first-class county.
Ben Slater (69), Wayne Madsen (58) and Matt Critchley (35) produced solid support, with Jonathan Trott (four for 65) the best Warwickshire bowler on show.
Sam Hain struck a classy 108 in response - his sixth list A century in only 30 games - but he received little support other than an unbeaten 48 from Keith Barker.
Warwickshire were finally dismissed for 300 after 45.3 overs, with Derbyshire debutant Safyaan Sharif impressing with his control and discipline in taking two for 31.
Leicestershire eased home by 72 runs at Northamptonshire after Paul Horton's 103 in 126 balls guided them to a challenging 265 for seven.
Northamptonshire have been badly short of runs so far this season and the County Ground faithful witnessed another miserable batting display.
Gavin Griffiths (four for 30) and Ben Raine (three for 31) did the damage as Northamptonshire slumped to 124 for eight.
Only late resistance from Graeme White and Brett Hutton, sharing 64 for the ninth wicket, avoided a complete humiliation before the hosts were dismissed for 193 in 38.2 overs.