Myburgh defiant while Durham fret about Onions
Somerset 147 for 4 (Myburgh 57*) trail Durham 189 (Jennings 49, C Overton 4-40) by 42 runs
For the second time this season Johann Myburgh defied one of his former counties, Durham, as he gave struggling Somerset a slight edge on the first day at Chester-le-Street.
After choosing to bat, Durham were dismissed for 189 with Craig Overton taking 4 for 40, then Myburgh followed the 115 he made against the same opponents at Taunton with an unbeaten 57.
Somerset were 147 for 4 at the close, while Durham had further cause to worry about Graham Onions. After missing much of last season through injury, he has already suffered three niggles this year and was off the field for most of the evening session.
Overton was the most impressive of those who might have interested watching national selector James Whitaker, although Durham's Chris Rushworth also bowled well. The first of his three victims took him to 100 championship wickets since the start of last season.
While his twin, Jamie, was left out to accommodate the return of Lewis Gregory, who proved expensive, Overton came on for the ninth over and took 2 for 19 in his first seven-over spell.
His fourth ball swung into left-hander Mark Stoneman to have him lbw and one which nipped back pinned Paul Collingwood in front for a duck.
From 46 for 3 Durham progressed to 117 through Keaton Jennings and Michael Richardson before four wickets went down for three runs in four overs after lunch.
Jennings was lbw trying to whip Tim Groenewald through mid-wicket and Jim Allenby somehow induced a ball to leap at Richardson, who fended to second slip, where Marcus Trescothick parried it and held on to the rebound.
Calum MacLeod sliced his second ball to backward point off Allenby then Paul Coughlin stayed on his crease and was lbw to Groenewald.
The slump was stemmed by a brief counter-attack from John Hastings as he Gordon Muchall shared a 50 stand in 48 balls before Overton yorked Hastings and forced Muchall to edge to Trescothick.
Trescothick survived a confident lbw appeal from Rushworth in the first over of the reply before the next big shout brought his downfall for 26 in the first over after tea.
Tom Abell had edged a drive at Rushworth to the wicketkeeper, but at 34 for 2 James Hildreth settled in cautiously. He had made six off 33 balls when he hit two fours and survived a chance to second slip, all in the same Hastings over.
After contributing 35 to a stand of 73 with Myburgh, Hildreth surrendered to Scott Borthwick's second ball, pulling a long hop straight to mid-on.
Tom Cooper did something similar, picking out mid-wicket off Rushworth, before Allenby kept Myburgh company to the close. Myburgh completed a 92-ball half-century with a four off Borthwick in the final over.