Moeen Ali in full flow steers Worcestershire Rapids to Finals Day

There is no more relaxed sight amid the frenzy of the Blast than Moeen Ali in full flow. An unbeaten hundred that stunned a capacity Hove crowd into silent admiration ensured that Worcestershire, the defending champions, returned to Finals Day as they subdued Sussex, the county they beat in last year's final, by eight wickets with 14 balls to spare.

No England player embodies his county more than Moeen. Others will briefly show their allegiance on their rare returns; Moeen somehow becomes Worcestershire, leading, spreading calm and seeking responsibility where on occasions with England he has failed to grasp it. The tranquil hitting that attracts so much criticism when it goes wrong looks so wonderful when it delivers.

Lacking overseas players Hamish Rutherford and Callum Ferguson and with Wayne Parnell, a key player with the ball this season, succumbing to illness, Worcestershire were vulnerable. But Moeen took another stroll down Easy Street, as if oblivious to the pressure.

The outcome was an unbeaten 121 off 60 balls, with 11 sixes and eight fours, an innings of gentle destruction which was the highest score of his T20 career and which made light of Sussex's more than respectable 184 for 6. The dew helped the ball skip on a little in the second innings, but it was helpful not decisive.

The winners of the North and South Groups, Lancashire and Sussex, have now both been eliminated with Worcestershire joining Essex and Notts at Edgbaston on September 21 and Gloucestershire and Derbyshire left to contest the last place at Bristol on Saturday.

Alex Hales and Chris Nash logged the Blast's highest partnership of the season on Thursday; 24 hours later, Moeen and Riki Wessels capped it with a stand of 177 in 17 overs. Moeen moved trance-like from 50 to 100 in 20 balls, caressing through the line as repeatedly cleared Hove's small boundaries with 15 metres to spare; Wessels ferreted around for 47 from 46 balls, an exercise based upon the urge to give Moeen the strike, before he pulled to deep square with six needed.

It could have been so different for Sussex. Reece Topley, who has been on painkillers to get through recent T20 matches, a sign that after five stress fractures the left-armer is still not free from injury fears, delivered the best two balls of the night in his opening over. Both swung late, the first hitting Joe Leach's off stump to end fond imaginings that his rustic pinch hitting might give Worcestershire a flyer, the second missing Moeen's off stump by a whisker.

The blemish that mattered, however, belonged to Alex Carey, Sussex's Australian keeper-batsman, who let a simple head-high catch through his hands after Moeen, on five, top-edged a pull against OIlie Robinson. Luke Wright, Sussex's captain, said simply: "Carey has got us to the quarter-finals. No blame attached."

Other opportunities were spurned, too, although by then the match was won. David Wiese, who had a bad night, allowed a catch through his hands when Moeen was 78, a pull to deep square against the legspinner Will Beer when Wiese never found a stable footing. Topley also spilled a skier off Danny Briggs at deep midwicket when Moeen was 108. In the next over, he rocked back to pull Robinson for six to claim the match.

"I'm a massive Mo fan," said Wright. "We had the best of him and we had no answer." What could Sussex have done differently? Perhaps bring back Robinson early because he, at that stage of the innings, had the potential to bowl an unplayable ball, rather than meet him with seven overs of spin in mid-innings. Or squeeze Wessels with tighter fields in the hope of a rush of wickets at the other end that might break Moeen's equilibrium. But they would have been faint hopes.

Sussex felt they had done enough with the bat. Reach the sudden-death phase of the Blast and there is nothing better than seeing your most dangerous batsmen spin the roulette wheel and see it come up in his favour. There is no more dangerous and yet vulnerable new-ball batsman in the Blast than Sussex's Phil Salt. In the circumstances, his fourth T20 half-century of the summer - 72 from 40 balls - felt like a shift in Sussex's favour.

Salt and Wright go together better than salt and pepper, the condiments to add flavour to Sussex's opening forays. Wright makes room to thrash the ball through the off side; Salt gets inside the ball and punts it to the leg side. Salt, on 19, was dropped at mid-on by Charlie Morris, playing his first T20 in three years. By the time Daryl Mitchell's mix-and-match dismissed both in successive overs, Sussex had 108 on the board after 10.3 overs.

Mitchell's intervention for the ninth over was a gamble: a runs-for-wickets intervention. Salt sent him for four leg-side sixes in no time, but by the end of his second over he had both openers on his card, Wright to a mishit to midwicket, Salt very well held by Wessels, running to his left at long-on.

That was the start of a regular loss of Sussex wickets with Ed Barnard, one of the most serviceable T20 cricketers in the Blast, also to the fore as he removed Carey and Wiese in the space of three balls, Carey lobbing up a slower ball as he tried to work it to backward square, Wiese clinically yorked.

Laurie Evans observed the casualties around him and remained a figure of total calm. That has not always been the case, but these days he is becoming a fixture on the T20 international circuit and is about to head to St Kitts and Nevis Patriots in the Caribbean Premier League. His unbeaten 41 from 31 balls was an innings played in the shadows. On many nights it would have been enough. But he couldn't account for Moeen.