Somerset fought back strongly with the ball and took a major step towards a Lord’s final after a dramatic Worcestershire collapse on the second day of the Bob Willis Trophy encounter at New Road.

The home side were threatening to post a formidable total after reaching 123 for one shortly after the lunch interval in reply to Central Group leaders Somerset’s 251 all out.

Jake Libby scored his fourth 50-plus score in eight innings in the competition, leaving the former Nottinghamshire player as the leading scorer in the Trophy with 475 runs at an average of 59.37.

But then the tables were turned spectacularly following an afternoon break for rain as nine wickets tumbled for 77 runs in 20 overs after tea, due to fine bowling by the pace trio of Craig Overton, Josh Davey and Jack Brooks mixed with some distinctly average shot selection.

Somerset lost Ben Green – bowled by Worcestershire captain Joe Leach for a duck – in reaching 16 for one before bad light ended play early.

They went into the game needing a maximum of 19 points to ensure their place in the final and the five bonus points already claimed means outright victory will seal a September 23 date.

Overton and Davey have a combined total of 47 wickets and an indication of the potency of Somerset’s attack is that Worcestershire’s total of 200 all out is the highest conceded by them in four-day cricket this summer.

But the clatter of wickets leaves them facing an uphill task, particularly with Josh Tongue unlikely to bowl after suffering a back spasm on the opening day.

Worcestershire resumed on 14 without loss on a pitch still offering some encouragement to the seamers.

Daryl Mitchell and Libby played positively before the former, on 31, was lbw to Lewis Gregory.

Spinner Jack Leach bowled tidily in his first competitive match for 10 months since being diagnosed with sepsis during England’s tour of New Zealand and then was laid low with a calf tear.

Libby released his control by straight driving a six and four in the same over but was fortunate when edging Brooks right through the hands of Leach at first slip.

The 27-year-old reached 50 off 114 balls, with one six and seven fours, before the players left the field half an hour into the afternoon session.

On the resumption, the pendulum swung decisively in Somerset’s favour.

Tom Fell went for 26 as a Brooks delivery shaped to move away but went straight on and dislodged a bail as he shouldered arms.

Jack Haynes lost his off stump to Gregory and Libby’s fine knock ended on 58 when he drove at Brooks and fell to a fine low catch by ex-Worcestershire keeper Steve Davies.

Riki Wessels’ aggressive approach paid dividends as he struck Brooks for five authentic boundaries in the space of 15 deliveries.

But Brett D’Oliveira was lbw to Overton and Wessels, having made 32 off 36 balls, went for a pull against the same bowler and fell to a fine catch at square leg by Ed Byrom.

Ed Barnard was bowled for a duck, aiming a blow on the leg side off Davey, and Ben Cox perished at third slip off Overton.

Davey had Joe Leach caught at first slip and bowled Tongue for the innings’ second duck and sixth single-figure score, with Dillon Pennington left stranded on 11 not out.

Green went with Somerset’s score on four but Tom Lammonby and captain Tom Abell saw them to an overnight lead of 67.