Surrey, Hampshire and Worcestershire Rapids all recorded victories on Friday evening to guarantee their qualification for the T20 Blast quarter-finals.
The two sides in the South Division narrowly got over the line against Gloucestershire and Sussex Sharks respectively, while Worcestershire thrashed Northants Steelbacks.
After Colin Munro (49) and Ben Cox (46) helped the Rapids post 162-9, Worcestershire captain Daryl Mitchell took 5-28, which included three caught and bowled dismissals, to secure his side a 31-run victory and put the holders on the verge of elimination.
Prolific opener Jason Roy missed out for Surrey at Cheltenham, but there were contributions from the whole batting lineup, with Tillakaratne Dilshan top scoring with 36, as the London outfit made 157-8.
Michael Klinger struck 45 opening for Gloucestershire, but Zafar Ansari claimed 3-37 to keep the home side behind the rate, and late hitting from Benny Howell (29) and Jack Taylor (19) was in vain as they came up five short.
Gloucestershire are unable to qualify for the next round, and neither are Sussex, who lost by six runs chasing down Hampshire's 177-3, which was inspired by Michael Carberry's unbeaten 87 and 52 from Jimmy Adams.
Luke Wright made 116 not out, but his teammates managed just 49 between them, with opening partner Chris Nash making 28 of those, as the Hove outfit were knocked out despite Wright's heroics.
New Zealand international spinner Jeetan Patel took a hat-trick as Birmingham Bears maintained their hopes of progressing to the last eight with a five-wicket triumph over top-four rivals Yorkshire Vikings.
Patel had Kane Williamson trapped lbw before bowling Andrew Gale and Adam Lyth with his next two balls on his way to becoming the joint-leading wicket-taker in the competition with figures of 4-19.
An unbeaten 69-run stand for the seventh wicket between Tim Bresnan (45*) and Adil Rashid (29*) helped the hosts post 147-6 at Headingley, and although Ryan Sidebottom helped reduce Birmingham to 40-4, Laurie Evans hit 69 from 44 balls to earn the Bears a crucial victory on the penultimate delivery.
Lancashire Lightning and Essex Eagles, leaders of the respective divisions, had already advanced to the knockout stages but their victories tonight mean that they will have home advantage in their quarter-final ties.
The Old Trafford outfit smashed North Group whipping boys Derbyshire Falcons all over the park to make a massive 225-7, with Ashwell Prince and Karl Brown each recording half-centuries.
Derbyshire gave it a good go, with Marcus North (41) and Wayne Madsen (45) dishing out some punishment of their own, but two wickets from overseas paceman Junaid Khan on his final Lancashire appearance of the year secured them their ninth win of the season.
The Eagles are the only side in the country who can better that tally, and they made it 10 victories from 11 this campaign by knocking off Glamorgan's 157-2 with eight seven wickets and two overs to spare.
Glamorgan only used three batsmen in their innings as Jacques Rudolph carried his bat for 60 from 57 balls and Murray Goodwin was caught on the final ball of their 20 overs for a more aggressive 71.
The Welsh outfit were made to rue not accelerating as Mark Pettini (28), Jesse Ryder (51) and Tom Westley (44) got Essex off to a fast start before Ravi Bopara completed the job with 32 not out.
A storm brought the match between Kent Spitfires and Somerset at Canterbury to a premature end, but enough overs had been bowled for the hosts to claim a 40-run win on the Duckworth-Lewis method.
Rob Key struck 72 and Sam Northeast 73 as Kent set their opponents a daunting 196 to win, and the former champions lost five wickets in seven overs to put them way behind the rate when the bad weather came.
Full results:
Worcestershire Rapids (162-9) beat Northants Steelbacks (131 a/o) by 31 runs.
Surrey (157-8) beat Gloucestershire (152-7) by five runs.
Hampshire (177-3) beat Sussex Sharks (171-8) by six runs.
Birmingham Bears (148-5) beat Yorkshire Vikings (147-6) by five wickets.
Lancashire Lightning (225-7) beat Derbyshire Falcons (190-7) by 35 runs.
Essex Eagles (159-3) beat Glamorgan (157-2) by seven wickets.
Kent Spitfires (195-7) beat Somerset (59-5) by 40 runs on Duckworth-Lewis method.
