Worcestershire 14 for 0 trail Somerset 251 (Abell 59, Pennington 3-49) by 237 runs
Somerset skipper Tom Abell continued his fine form in the Bob Willis Trophy by top-scoring on the opening day of a see-saw crucial Central Group clash with Worcestershire at Blackfinch New Road.
Abell showed his class in striking 59 to help ensure his side posted a challenging total on a green-tinged pitch offering encouragement to the seamers. It followed on from his 119 against Glamorgan and an unbeaten 101 versus Gloucestershire earlier in the competition as Somerset totalled 251 all out in 83.1 overs.
Worcestershire continued to probe away, despite the absence of paceman Josh Tongue with a back spasm for the second half of the day, with Dillon Pennington and Ed Barnard picking up three wickets.
A spell of five wickets for 41 runs in 18 overs tipped the game in Worcestershire's favour as Somerset collapsed to 134 for 6. But steady lower-order contributions from Lewis Gregory, Josh Davey and Jack Leach steered the visitors to two batting points.
Worcestershire openers Daryl Mitchell and Jake Libby then survived five probing overs from Craig Overton and Josh Davey in reaching 14 for 0.
Worcestershire made one change from the side which drew with Warwickshire with Pennington replacing fellow paceman Charlie Morris.
The visitors made two changes from the team victorious over Gloucestershire - both of them enforced - with Ben Green and Jack Leach in for the injured James Hildreth (hamstring) and Jamie Overton who has joined Surrey on loan prior to a permanent move.
The initial breakthrough for Worcestershire was self-inflicted by Somerset with Green run out for 8 with 18 on the board. Tom Lammonby played Tongue into the covers and set off instantly for what looked a risky single - and Green was unable to beat Barnard's direct hit.
There was plenty of playing and missing during the morning session but also some fine stroke play from Abell who dominated a partnership of 75 in 26 overs with the resolute Lammonby. The opener, on 12, had a let off when Riki Wessels at first slip failed to hold onto a low chance low to his left off Pennington.
The second-wicket pair continued to prosper and Abell reached his half century off 89 balls with eight fours just after lunch. But Pennington, who delivered an excellent eight-over post-interval spell, broke the stand when Lammonby chopped a delivery on to his stumps.
George Bartlett departed in similar fashion to a ball from Tongue and then Pennington picked up the prized wicket of Abell. He found the edge of his bat and keeper Ben Cox pulled off a fine low catch away to his right.
Spinner D'Oliveira came into the attack and struck in his first over when bowling former Worcestershire wicketkeeper batsman Steve Davies through the gate.
It became 134-6 when Craig Overton edged Barnard and perished to a low catch by Daryl Mitchell at second slip. But Gregory then went on the offensive with a trio of sixes - including two in an over from Barnard - and he and Eddie Byrom added 61 in 15 overs.
Gregory became tied down by D'Oliveira after tea and the spinner was rewarded when he sliced his attempted drive into the hands of Pennington at short third man.
Pennington struck with the ball for the third time when Byrom attempted a cut shot and Barnard pulled off a magnificent catch low down at point. Davey holed out to square leg off Barnard - his 200th first class wicket - and the same bowler trapped Jack Leach lbw to wrap up the innings.