Last year: 8th in North Group
Captain: Will Rhodes
Coach: Jim Troughton
In a nutshell: Hopeless last year with 19 players used and no obvious strategy with bat: dropping firestarter Ed Pollock after four failures to accommodate Dom Sibley as a second anchor in the top three was a fatal error. Chris Green was due to captain but is playing in the CPL instead, but the majority of last year's squad will be available throughout.
Star: Pollock's omission was a source of frustration to sporting director Paul Farbrace last year, and he should get a chance to play all ten group games at the top of the order. He is the fastest-scoring batsman in the world, and told ESPNcricinfo during lockdown of his intentions to turn "flashes in the pan" into the sort of innings "that make someone go: 'we want him'". With his contract up at the end of the season, the pressure is on.
One to watch: Henry Brookes was the Bears' leading wicket-taker last year and proved particularly effective at the death: in 11.4 overs at the back-end, he took eight wickets and went at only 7.45 runs per over. He brings genuine pace to the attack, with Olly Stone missing the start of the tournament through injury.
Verdict: Decent side on paper but need to hit the ground running
Last year: 9th in South Group
Captain: Chris Cooke
Coach: Matt Maynard
In a nutshell: Rock-bottom last year, and winless until the final game of the group stage. Colin Ingram, who has been their key man with the bat in recent seasons, is "unlikely" to arrive due to travel restrictions, according to Mark Wallace, the director of cricket, but otherwise availability is fairly good.
Star: With Ingram absent and David Lloyd injured, much of the run-scoring burden with fall on Ireland captain Andy Balbirnie, a late overseas signing for the competition. A useful anchoring batsman, Balbirnie is likely to bed in at No. 3 and hold the innings together, generally ticking over at a strike rate around 140. He is no stranger to Wales, having attended Cardiff Met back in his university days.
One to watch: Callum Taylor was given four games to impress at the end of last year's tournament, but it is his red-ball form that suggests he could be a useful inclusion this year, after he thrashed 106 off 94 balls on first-class debut this week. His form in the Second XI T20 has been patchy over the last two years, but he should get a decent run in the side.
Verdict: Few obvious signs that last year was an outlier
Last year: 2nd in South Group, quarter-finalists
Captain: Jack Taylor
Coach: Richard Dawson
In a nutshell: Until they forgot to turn up in the home quarter-final against Derbyshire, Gloucestershire had an impressive 2019 in the Blast, and were only narrowly pipped to top spot in the South Group. Much-loved captain Michael Klinger misses the Blast for the first time since 2012 after his retirement, but that could be a blessing in disguise after his slow-scoring became a hindrance last summer.
Star: Slower-ball specialist Benny Howell had his tournament cut short by a hamstring injury sustained at The Oval last year, and has not made a professional appearance since then. In 2019, he had 10 wickets and a miserly economy rate of just 6.65 before his injury. He will miss out on the early stages due to a suspected calf tendon tear but hopes to return for the back end.
One to watch: James Bracey has spent the summer wearing blue latex gloves and carrying the drinks for England in the Test bubble, so will be desperate to get onto the field in the Blast. He could open alongside Miles Hammond this year in an anchoring role, and is a useful player on difficult pitches.
Verdict: Often written off, usually wrongly
Last year: 7th in North Group
Captain: Josh Cobb
Coach: David Ripley
In a nutshell: Neutrals' favourites and two-time winners, Northants have had three poor years in the Blast since their memorable title charge in 2016. There are reasons for optimism this year: their likely top four of Richard Levi, Paul Stirling, Josh Cobb and Adam Rossington packs an almighty punch, with Alex Wakely set to bat at No. 5. The big question is whether they have the bowling attack to compete.
Star: Josh Cobb has a point to prove after surprisingly missing out on selection in last year's Hundred draft, and will lead the side again this season. He warmed up with 80 off 45 and 33 off 14 in back-to-back practice fixtures against Leicestershire, and his offbreaks are a valuable early weapon in the first six overs.
One to watch: South African-born seamer Brandon Glover was joint-second in the wicket-taking charts in the T20 World Cup qualifier for Netherlands last year, and hits a hard length at good pace. He was particularly effective in the middle overs in that tournament, but may be required at the death in the Blast.
Verdict: Dark horses for the title
Last year: 6th in South Group
Captain: Lewis Gregory/Tom Abell
Coach: Jason Kerr
In a nutshell: Had competition's two leading run-scorers last season in Babar Azam and Tom Banton, while Tom Abell enjoyed a breakout T20 campaign that won him a £100,000 deal in the Hundred. But they were let down by their bowling attack, and with question marks over key players' availability this year - Banton and Lewis Gregory will miss at least the first few games due to England inclusion - it may be another disappointing year.
Star: He will miss the first few games due to Pakistan's T20I series against England and the club are yet to confirm his availability, but it is understood Babar is likely to play a handful of group games at the very least. In a tournament short on overseas quality due to restrictions on international travel and budgets, he should be just as dominant as he was in 2019.
One to watch: The Blast's leading legspinner over the last five seasons (66 wickets at 25.63), Max Waller rarely attracts much attention outside of Somerset, but is a proven operator and has been particularly useful with the new ball in recent years (10 Powerplay wickets with a 6.31 economy rate since 2017). He could be the best fielder in county cricket, too, as his one-handed screamer off AB de Villiers last year demonstrated.
Verdict: Belligerent at Taunton but attack lacks bite
Last year: 4th in North Group, runners-up
Captain: Moeen Ali/Ed Barnard
Coach: Alex Gidman
In a nutshell: 2018 champions were one dot ball away from repeating their triumph in last season's final, but fell at the final hurdle. Wayne Parnell is a big miss, while Pat Brown misses the first handful of games on England duty and Moeen is unlikely to feature at any stage. Canny allrounder Ed Barnard has been handed the captaincy in his stead.
Star: Nobody has scored as many Blast runs as Riki Wessels since 2014 (2656 at 35.89, 146 SR) and his runs were vital last season in a more restrained role than the one he used to play at Nottinghamshire. He looks set to open alongside Hamish Rutherford, one of the competition's few overseas players, in a partnership that should score the bulk of Worcestershire's runs between them.
One to watch: Daryl Mitchell found himself languishing down the batting order last season but has reinvented himself as a cutter specialist, rarely reaching 70mph with his medium pace and proving difficult to hit with Ben Cox stood up to the stumps. Last season, he conceded just 6.41 runs per over across the Blast, and is a brilliant option on slow wickets.
Verdict: If Brown is released after England's Pakistan series, knockouts should be within reach
Matt Roller is an assistant editor at ESPNcricinfo. He tweets at @mroller98