Forge Valley produced a huge shock, beating Premier Division champions Staxton by 19 runs.
Sean Pinder top-scored with 66 in Valley's 166-9, Will Tindall also adding 32, with Dan Outhart (2-22) and Adam Hargreaves (2-29) impressing with the ball for Staxton.
Tyler Beck the stunned Staxton's batting line-up, claiming 5-34 alongside Pinder (3-23) as only Liam Scott (29) got going with the bat as they crumbled to 147 all out.
Staithes failed to capitalise on Staxton's defeat as they lost their first game of the season by just nine runs at Nawton Grange.
Grange posted 149-9, Jonny Pickard hitting 50 and Jodie Robson 33, before Staithes were all out for 140 in reply, agonisingly short of their target.
Two other sides who are fancied to mount an outside challenge for the title met, with Filey sealing a comfortable 79-run win at home to Seamer.
Filey posted an imposing 231-6, in-form Ryan Baldry their top-scorer with 51, while he received good support from Josh Dawson (46), Nathan Robson (43no) and skipper Dave Brannan (38).
Aussie all-rounder Tom Fitzgerald then did the damage with the ball, taking 6-46 to ensure Seamer were all out for 152, Mitch Fisher hitting 50 of those runs.
There were comfortable victories elsewhere in the Premier Division for Cayton, Ebberston and Scalby.
James Small and Jake McAleese were the star men for Cayton in their 119-run success against Mulgrave.
Aussie Small smashed 70 in Cayton's first innings knock of 227 all out, Michael Dennis adding 56 and Harry Holden 40 as Chris Knight took 3-23 and Andrew Cass 3-50 for the Lythe-based visitors.
Mulgrave's batsmen had no answer to the bowling of McAleese (5-23) and James Ward (3-41) as they were bowled out for just 108 in their reply.
In a crucial game at the bottom end of the Premier Division table, Scalby cruised to a seven-wicket success at home to promoted Thornton Dale.
Dale elected to bat first and were looking in a healthy position to post a competitive total as Lewis White (48) and Tim Hunt (42) contributed good runs at the top of the order.
Scalby spinners Lachlan Cooke (4-34) and Paul Hesp (2-20) ensured the visitors were pegged back though as they collapsed to 131 all out.
Fourteen-year-old Ed Hopper then shone with the bat in Scalby's reply, hitting a composed 47 with support from fellow-opener Dave Holborn (28) and Adam Waugh (32no) as the hosts made it comfortably to their victory target.
Jonny Mason was the star man in Ebberston's 85-run win at Heslerton.
Mason's knock of 87 helped Ebberston post 236-9, Tom Brickman also hitting 57 as Paul Kinghorn (5-38) and Andy Slaughter (3-53) were in good form with the cherry.
Despite Sam Triffitt hitting 49 and Simon Oxendale 34, Aussie Cooper Barnes took 3-39 to help restrict the hosts to 151-9.
In a high-scoring encounter in Division One, Great Habton stayed top of the pile after a six-run win at Flixton 2nds.
John Lumley (57), Will Curtis (35no), Ed Cass (34) and Doug Bentley (31) all contributed to Habton's 229-6, Noman Shabir taking 2-26.
Carl Sample was on song with the bat in reply, hitting an unbeaten 60, with Shabir and Anderson adding 58 and 40, but Jim Boyes took 5-45 to ensure Flixton fell agonisingly short on 223-8.
Brompton cruised to a 10-wicket success at struggling Staxton 2nds, with Mark Bruce in imperious form with the bat for the victors.
Staxton posted 145-5, Nigel Pinfield hitting 44, Stephen Beal 30 and Mark Dove 28.
That proved to be nowhere near enough for victory, Bruce hitting a stunning unbeaten 91 and Robin Siddle remaining not out on 50 at the other end as Brompton cruised to 150-0.
Cloughton also cruised to a comfortable win, beating Sherburn by eight wickets.
Craig Sanderson smashed 70 and Mike Holtby added 25, but Jon King's 3-42 pegged them back to 145 all out.
Cloughton's reply was emphatic, Aaron Virr hitting 57 and Ricky Nock an unbeaten 47 as they cruised to 149-2.
Wykeham beat promoted Ganton by 40 runs.
Mike Dugdale top-scored for the hosts with 38 in their total of 154-8, Steve Clegg also hitting 36 not out. Greg Cousins (3-22) and Will Bradley (3-27) picked up decent figures with the ball.
Robbie Milner hit 48 for Ganton, but impressive bowling from Matty Vincent (4-25) and Dave Pearson (4-36) saw the visitors all out for just 114.
*Filey 231-6 (Ryan Baldry 51, Josh Dawson 46, Nathan Robson 43no, David Brannan 38) beat Seamer 152 all out (Mitch Fisher 50, Tom Fitzgerald 6-46) by 79 runs. Pts 22:7
*Forge Valley 166-9 (Sean Pinder 66, Will Tindall 32, Dan Outhart 2-22, Adam Hargreaves 2-29) beat Staxton 147 all out (Liam Scott 29, Jack Pinder 21, Tyler Beck 5-34, Sean Pinder 3-23) by 19 runs. Pts 22:8
Ebberston 236-9 (Jon Mason 87, Tom Brickman 57, Paul Kinghorn 5-38, Andy Slaughter 3-53) beat *Heslerton 151-9 (Sam Triffitt 49, Simon Oxendale 34, Cooper Barnes 3-39) by 85 runs. Pts 20:11
Cayton 227 all out (James Small 70, Mike Dennis 56, Harry Holden 40, Chris Knight 3-23, Andrew Cass 3-50) beat *Mulgrave 108 all out (Jake McAleese 5-23, James Ward 3-41) by 119 runs. Pts 22:8
*Nawton Grange 149-9 (Jonny Pickard 50, Jodie Robson 33) beat Staithes 140 all out by 9 runs. Pts 22:8
*Scalby 132-3 (Ed Hopper 47, Adam Waugh 32no, Dave Holborn 28) beat Thornton Dale 131 all out (Lewis White 48, Tim Hunt 42, Lachlan Cooke 4-34, Paul Hesp 2-20) by 7 wkts. Pts 22:4
Great Habton 229-6 (John Lumley 57, Will Curtis 35no, Ed Cass 34, Doug Bentley 31, Noman Shabir 2-26) beat *Flixton II 223-8 (Carl Sample 60no, Noman Shabir 58, Cameron Anderson 40, J Boyes 5-45) by 6 runs. Pts 20:11
Cloughton 149-2 (Aaron Virr 57, Ricky Nock 47no) beat *Sherburn 145 all out (Craig Sanderson 70, Mike Holtby 25, Nick Dobson 22, Jon King 3-42) by 8 wkts. Pts 22:4
Brompton 150-0 (Mark Bruce 91no, Robin Siddle 50no) beat *Staxton II 145-5 (Nigel Pinfield 44, Stephen Beal 30, Mark Dove 28) by 10 wkts. Pts 20:5
*Wykeham 154-8 (Mike Dugdale 38, Steve Clegg 36no, Greg Cousins 3-22, Will Bradley 3-27) beat Ganton 114 all out (Robbie Milner 48, Matty Vincent 4-25, Dave Pearson 4-36) by 40 runs. Pts 22:6