|Specsavers County Championship Division One, Emirates Old Trafford, day three|
|Somerset 553-8 dec: Trego 154, Abell 135, Davies 86, Trescothick 60; Bailey 5-111|
|Lancashire 422-9: Petersen 155, Croft 58, Livingstone 57, Hameed 56; Gregory 3-74|
|Lancashire (5 pts) trail Somerset (5 pts) by 131 runs|
Alviro Petersen made his third County Championship century of the summer as Lancashire batted all day at Old Trafford to successfully avoid the follow-on at home to Somerset.
Resuming on 138-2 in reply to Somerset's 553-8 declared, Petersen (155) shared century stands with Liam Livingstone (57) and Steven Croft (58).
Petersen and Croft were then both out in the space of six balls.
Although Luke Procter went cheaply, Lancashire closed safely on 422-9.
Somerset lead by 131 runs going into the final day but, with rain forecast in Manchester, a draw looks almost certain.
After losing just one wicket in the first two sessions, the evening session proved dramatic by comparison as the end of the 157-run stand between Petersen and Croft triggered the fall of six wickets, three of them for visiting paceman Lewis Gregory.
But the hosts reached the close with Tom Bailey on 17 and last man Toby Lester still to score on his first Championship appearance for a year.
Both sides would receive 10 points if the game is drawn, to further improve their hopes of staying in Division One.
Lancashire centurion Alviro Petersen told BBC Radio Lancashire:
"We started off by saying that we wanted to bat the whole day because that was the only way in which we could avoid the follow-on. There were some decent partnerships and we've done that.
"Somerset ensured we couldn't win the game but it's pretty tough when the follow-on is 400 runs away but it's the sort of wicket that, if you get into a partnership, the easier it becomes to score runs.
"It was nice that the top order took responsibility. In cricket, you're never satisfied but I think that the season has gone all right for me but it's not about personal achievements."