Last year: 3rd in North Group, semi-finalists
Captain: Billy Godleman
Coach: Dominic Cork
In a nutshell: Derbyshire are "#UnderestimatedNoMore", at least according to their social media campaign ahead of this tournament - we boldly stated in last year's preview that they "have never reached Finals Day and that is not about to change", only for them to turn Gloucestershire over at Bristol to reach the semis. Last year's top wicket-taker Ravi Rampaul is stuck in Trinidad due to travel restrictions and hopes to arrive later in the season, and playing every game away while Derby is used as a biosecure base for Australia men and then England women is a major disadvantage.
Star: Wayne Madsen had an unbelievable tournament in 2019, combining consistency (46.40 average) with fast scoring (147 strike rate). He is particularly effective against spin, scoring freely in the middle overs, and forms a formidable top four alongside Billy Godleman, Luis Reece and Leus du Plooy.
One to watch: Young legspinner Matt Critchley signed a new contract last month with reports of interest from other counties, and was the key in the middle overs in 2019 when he took 17 wickets at an economy rate of just 7.13. His batting was less impressive, but he has the levers to succeed as a finisher if he is backed.
Verdict: Write them off at your peril
Last year: 6th in North Group
Captain: Nathan Rimmington
Coach: James Franklin
In a nutshell: Heavily reliant on D'Arcy Short last season, and short of star quality this time around. Their bowling attack has some firepower, and should do well on slow home pitches, but it is difficult to see how they can succeed in Short's absence.
Star: Scott Steel was Short's opening partner last season and had a breakout tournament with 369 runs and a useful strike rate of 137. He has been working on his game against spin this year, and is aware that it will be harder to back up his performances with teams analysing his weaknesses. He chipped in with the ball, too, taking five wickets with his offbreaks.
One to watch: After two injury-hit years at Nottinghamshire, Paul Coughlin is back at the club where he broke through as a hard-hitting allrounder. There will be extra emphasis on his batting this year, but he warmed up for the tournament with a fluent 90 in the Bob Willis Trophy draw against Derbyshire this week.
Verdict: Unlikely to qualify from a strong group
Last year: 1st in North Group, quarter-finalists
Captain: Dane Vilas
Coach: Glenn Chapple
In a nutshell: Dumped out by Essex in the quarters in 2019 after a near-faultless group stage, and well-placed to do well again this year if England call-ups permit. Expect spin to play a major role again, with Matt Parkinson on his way back from injury, while young players like Tom Hartley and Josh Bohannon should get chances to impress. Liam Livingstone and Saqib Mahmood start the tournament with England, but should return later in the group stage.
Star: Parkinson has missed out on England's white-ball squads so far this summer due to injury but was back training with the squad at Headingley this week and should be fit for most of the competition. No spinner has as many wickets (63) in the last three seasons of the competition and it will be interesting to see if he has developed any new variations over the winter.
One to watch: After his eyebrow-raising early pick-up in the Hundred draft made him the butt of several jokes, Dane Vilas will be keen to remind people of his worth as a T20 player. He was a key component in their side last year, striking at 146 in the middle order and earning praise for his captaincy right up until the crucial moment in the quarters against Essex.
Verdict: Fitness and availability will be key to their fortunes
Last year: 9th in North Group
Captain: Colin Ackermann
Coach: Paul Nixon
In a nutshell: Rooted to the bottom of the North Group last season, with Ackermann's world-record 7 for 18 against Birmingham Bears a rare bright moment. Mark Cosgrove is a big absence in more ways than one, and the spin attack of Ackermann, Callum Parkinson and Arron Lilley will be key.
Star: Most teams slow down after the end of the Powerplay, but Lilley's impetus at No. 3 means that has rarely been the case for his sides. Last year, he scored at 10.15 runs per over in overs 6-12, and his ability to hit boundaries against both pace and spin makes him a valuable asset.
One to watch: Gareth Delany underwhelmed in Ireland's ODI series in England this summer, but he demonstrated his power-hitting credentials in the T20 World Cup qualifier last year, and when thumping West Indies legspinner Hayden Walsh Jr. for four consecutive sixes at the start of 2020. His unique backlift means he can look ungainly at the crease, but he is an explosive talent who can chip in with some legbreaks as well.
Verdict: Will cause a shock or two but quarters look beyond them
Last year: 2nd in North Group, semi-finalists
Captain: Dan Christian
Coach: Peter Moores
In a nutshell: All set to cruise into the final last season before a dramatic implosion saw them beaten by one run against Worcestershire. They are perhaps the Blast's strongest team on paper, despite Harry Gurney's injury, with Dan Christian and Alex Hales added to a talented group of young batsmen including Joe Clarke, Ben Duckett and Tom Moores.
Star: Alex Hales is the bookies' favourite to lead the run-scoring charts this season, and with good reason after his exploits on the T20 circuit - between the start of last year's Blast and the end of this year's PSL, nobody played more games or scored more runs in the format. He is particularly brutal at Trent Bridge, where he has a 178 strike rate over the last three years, and Notts play six of their 10 group games there.
One to watch: Matt Carter, the 'Bardney Bamboozler', was the star with the ball in 2019, finishing with 14 wickets and a frugal economy rate of 6.59 despite bowling 45% of his overs in the Powerplay. Missed the last Bob Willis Trophy game through injury but should be fit for most of the tournament, and has been included in the squad for the first game.
Verdict: Finals Day is the minimum expectation
Last year: 5th in North Group
Captain: David Willey/Tom Kohler-Cadmore
Coach: Andrew Gale
In a nutshell: Never recovered after a slow start last season but look incredibly strong when everyone is available this year. The big question is how often that will be the case, with Jonny Bairstow, Joe Root, Dawid Malan, Adil Rashid and new captain David Willey all likely to miss several games due to England selection.
Star: Tom Kohler-Cadmore will captain the side when Willey is not around, and did a brilliant job at the top of the order with Adam Lyth last season, making 435 runs at 62.14 and striking at 141. He is comfortable against both spin and pace and may have to score the bulk of the runs while others are on international duty.
One to watch: The bowling attack looks light on paper following Tim Bresnan's departure over the winter, so this would be a good time for young allrounder Jordan Thompson to step up. He has started the season strongly in red-ball cricket, and has shown his finishing credentials in second XI cricket over the last two seasons.
Verdict: Need to start well to lay the foundation before England players return