Kent Spitfires became the latest side to reach the T20 Blast quarter-finals ending holders Essex Eagles' slim hopes of retaining the trophy in the process.
Elsewhere Notts Outlaws saw their unbeaten run ended by neighbours Leicestershire Foxes and Lancashire fell to a record defeat by Durham.
Somerset also won again to keep their quarter-final hopes alive.
Three quarter-final spots will still be up for grabs when the final group matches take place on Sunday.
Securing home advantage will also still be on the line for the five sides already through - Kent, Surrey, Lancashire, Notts and Gloucestershire - after defeats for a couple of in-form sides.
Despite progressing earlier this week, Gloucestershire, Lancashire and Notts Outlaws all found themselves on the wrong end of results.
While other sides won to give themselves an outside chance of a place in the knockout stages, they may still need to rely on other results even if they win again on Sunday.
Spitfires beat old enemy to qualify
In one of Friday's early games, Kent edged out Essex in a tense encounter at Canterbury.
The hosts chased their target of 168 with two balls to spare thanks to Jack Leaning's unbeaten 55.
He and Alex Blake (29) rescued them from a precarious 80-5 to add 67 for the sixth wicket before Grant Stewart struck the winning six to eliminate holders Essex.
Top place in the South Group will be decided on Sunday when Kent travel to in-form Surrey. Their sixth successive win came against Hampshire by an impressive nine-wicket margin.
Laurie Evans (81 not out) and Will Jacks (56 not out) shared an unbeaten 118 as they made light work of Hampshire's under par 138-8.
Reece Topley also returned to haunt his former employers with a career-best 4-20 with the ball.
Third-placed Sussex beat Middlesex to put themselves within touching distance of the last eight.
Left-arm seamer George Garton took 4-27 and then struck a decisive 24 off just nine balls as the Sharks chased 156 with four balls to spare despite a middle-order collapse.
Opener Phil Salt also made 56 off 40 balls as he returned to county colours.
A win for Sussex at Essex on Sunday could see them finish second, but they could also still go through as one of the two best third-placed sides even with a defeat.
Four central teams chase two potential spots
There may well need to be a bit of number-crunching come Sunday's final Central Group matches with a three-way tie for second place still a possibility.
Leaders Gloucestershire were unable to book a home quarter-final as they fell 17 runs short against Glamorgan.
Ireland's Andy Balbirnie made 99 not out from 54 balls in their impressive 188-4. Knocks from Chris Dent (55) and James Bracey (37) were not enough as Graham Wagg took 3-34.
Meanwhile Birmingham Bears, Northamptonshire Steelbacks and Somerset could all still go through and depending on how results go in the other two groups.
The Bears' 16-run win against Worcestershire Rapids at Edgbaston gives them a two-point advantage over Somerset and Northants in third and fourth.
Sam Hain (60) and Dan Mousley (40) helped the hosts post 179-6 and despite 45 off 23 balls from Hamish Rutherford and Brett D'Oliveira's 61 off 40 balls, Worcestershire could only make 163-8 in reply.
Somerset leapfrogged Northants courtesy of their impressive seven-wicket win at Taunton.
Tom Lammonby (43 not out) and captain Tom Abell (42 not out) backed-up Steven Davies' 45 to make light work of a target of just 141.
Lewis Gregory's return from England duty continued to prove pivotal as he claimed 2-22.
But who goes through from that group is likely to hinge on Northants' match at Birmingham Bears while Somerset head to Gloucestershire.
Off-boil Lancashire have night to forget
Lancashire sealed their quarter-final place on Thursday beating rivals Yorkshire by just seven runs.
But 24 hours later, they were considerably second best against Durham.
After Alex Lees made 67 not out to help Durham post 162-7, Matty Potts gave them a dream start with the ball.
He took three wickets in five balls to reduce the Red Rose to 9-4 from which they never recovered. Lancashire were later dismissed for a county-record low of just 83 in 15 overs.
Potts took a career-best 3-8 and insult was added to injury for Lancashire when they conceded five penalty runs when Liam Livingstone was reprimanded for using foul and abusive language after being dismissed by Paul Coughlin.
The win keeps Durham's quarter-final hopes alive and they will travel to group leaders Notts on Sunday.
Another side also still in with a chance of making the quarter-finals is Leicestershire after their four-wicket win inflicted a first defeat of the season on Notts.
Colin Ackermann ultimately proved the match-winner with his unbeaten 67 off 53 balls after the Foxes' chase of 163 looked in trouble at 113-5 with six overs to go.
But penalty runs also played a part in this match as Leicestershire were awarded five runs in the first over of their innings.
Umpires Nick Cook and Paul Pollard ruled Outlaws all-rounder Steven Mullaney had contravened the law by simulating the action of sliding and grabbing the ball in a way that, in their judgement, could have deceived opener Nick Welch.
Callum Parkinson later scampered through for the winning single as Alex Hales missed a chance for a direct hit run out off the penultimate ball.
But Leicestershire will still need a big win over Lancashire and probably several other results to go their way on Sunday to progress.
All four quarter-finals take place on Thursday, 1 October, two days before Finals Day at Edgbaston.
Bristol: Gloucestershire v Somerset
Edgbaston: Birmingham v Northamptonshire
Worcester: Worcestershire v Somerset
Headingley: Derbyshire v Yorkshire
Old Trafford: Lancashire v Leicestershire
Trent Bridge: Notts Outlaws v Durham
Chelmsford: Essex v Sussex
Ageas Bowl: Hampshire v Middlesex
The Oval: Surrey v Kent