Never good enough to reach finals day in nine years of trying, never good enough even to earn a home quarter-final, Yorkshire will at least enjoy that privilege when they face Worcestershire at Headingley. Unless the form that has won them seven from eight completed matches in the North Group deserts them at the critical moment, it is hard to imagine that Yorkshire will not go to finals day in the Friends Life t20 in Cardiff on August 25, and possibly as favourites.

The Yorkshire transformation has been by some margin the eye-opener in a competition that has found it difficult to attract attention in a damp and chilly summer amid a congested calendar of sport. Some say it is down to the experience brought together in a management trio teaming Jason Gillespie and Paul Farbrace with the established wisdom of Martyn Moxon, others that the signing of two overseas players at the hungry end of their international careers has been the key.

While both of those arguments have their strengths, there is another that can be tossed into the debate, namely the appointment of Azeem Rafiq as temporary captain after Andrew Gale dropped out with a hip injury after the third group match. Aged only 21, which made him the youngest player in the county's history to captain the senior side, Rafiq's elevation might be seen as shrewd judgment or a lucky gamble but there is no doubt it has paid off handsomely.

Given that he had led England sides and Under-15 and Under-19 level and captained Yorkshire in second XI and pre-season matches the gamble was smaller than some might have supposed, although his senior experience was naturally quite limited.

Yet Gillespie claimed "it took about five seconds" to conclude that Rafiq was the right man for the job and after five wins from seven completed matches with him in charge, including a comprehensive six-wicket win over strongly fancied Nottinghamshire at Trent Bridge, it is hard to criticise the Yorkshire hierarchy for making a hasty judgment. When the now recovered Gale returns to lead the side against Worcestershire it will be with a fulsome endorsement of his stand-in.

"What I like about Azeem is that I see a bit of myself in him," Gale said of Rafiq, whose heritage also makes him the first cricketer of Asian origin to captain Yorkshire. But it is not only the "aggressive, up-and-at-'em in-your-face" approach that has impressed Gale. His tactical judgment has also met with approval.

"When I am out on the pitch, he comes to me all the time suggesting things," Gale added, in his weekly newspaper column. "Some lads suggest things and you think: 'No, that's not right.' But what I've found nine times out of 10 is that what he suggests is what I'm thinking. I think we're on the same wavelength."

Moxon, Yorkshire's director of professional cricket, believes keeping to a pre-meditated game plan made it easier for Rafiq but that he took on the responsibility impressively nonetheless. "He's got a good cricket brain, and he keeps calm under pressure, which you need to do as a captain," Moxon said. "We've got a set plan on how we want to play, which makes it easier for him in the sense of the bowlers knowing what we're trying to do. But he's a great motivator in the field."

It is extraordinary to recall now that Rafiq's debut for Yorkshire in 2008 cost them a Twenty20 Cup quarter-final after his appearance in a group stage win over Nottinghamshire. Then an academy player, he was selected in good faith but questions over his eligibility led to Yorkshire's quarter-final against Durham being postponed moments before it was due to begin and ultimately their effective disqualification after the result at Trent Bridge was reversed.

If that were a controversy not of his making, the same cannot be said of the error of judgment he made two years ago when an outburst on Twitter against coach John Abrahams on being dropped from an England Under-19 side on disciplinary grounds led to a one-month ban from all cricket. Clearly he has acquired some maturity since then.

Worcestershire, having qualified as one of the two best third-placed sides from the group stages, are also bidding to reach finals day for the first time in the 10 years of Twenty20. They might appear to have weaker credentials than Yorkshire, but they emerged from a strong Midlands/Wales/West Group headed by Somerset and Gloucestershire, finishing level with Warwickshire on 11 points but with a better net run rate.

What's more, they possess the 2012 competition's highest run scorer in opener Philip Hughes, who has hit three half-centuries in an aggregate of 322 from seven innings. Yorkshire, on the other hand, have been well served by several players.

Opening batsman Phil Jaques has shared two hundred-plus partnerships - 118 with Gale against Leicestershire at Headingley and 131 with Adam Lyth in the concluding group match against Derbyshire, also at the Leeds ground. David Miller, the 23-year-old South African who forms one half of their overseas duo, hit 28 runs in the last two overs against Durham at Chester-le-Street to finish 74 not out from 35 balls and shared a stand of 91 in 7.1 overs with Gary Ballance against Lancashire at Headingley, in front of a crowd of 10,350.

The Australian fast bowler Mitchell Starc, 22, meanwhile, is the competition's leading wicket-taker with 18 and has been particularly effective at the end of an innings. There is a question mark over Starc's availability for finals day after he was called up to Australia's one-day and Twenty20 squads for their series against Pakistan in the UAE, which includes a one-day international against Afghanistan in Sharjah on August 25.

Nottinghamshire's surprise home defeat to Yorkshire did not preclude them also securing a home quarter-final with Hampshire in the other Wednesday tie. It was their only defeat in 10 North Group matches and, with Alex Hales, Michael Lumb, Riki Wessels, Adam Voges, Samit Patel and James Taylor presenting as the strongest top six in the country, they will start as strong favourites, although Glenn Maxwell, the batsman named in Australia's provisional squad for the World Twenty20, could be a dangerous opponent, especially with Darren Pattinson, a key Nottinghamshire bowler in this competition, failing to recover from a groin injury suffered in a CB40 match on Sunday.