Lancashire 193 for 6 (Jennings 60, Carson 4-50) trail Sussex 328 (van Zyl 79, Haines 58) by 135 runs
Young off-spinner Jack Carson continued his impressive start to the season with four wickets as Sussex fought back strongly against Lancashire in the LV=Insurance County Championship Group 3 match at Hove.
The 20-year-old from Northern Ireland finished the second day with 4 for 50 from 28 overs as Lancashire reached 193 for 6 in reply to Sussex's 328, having been 137 for 1.
Carson now has 15 wickets this season while 18-year-old debutant Jamie Atkins also had cause for celebration after removing Lancashire skipper Dane Vilas for a duck to claim his maiden first-class scalp.
Lancashire openers Alex Davies and Keaton Jennings had put on 93 with few alarms with Jennings passing 50 for the first time this season, but Carson broke through in his fifth over when a quicker ball deceived Davies, who chopped on trying to cut after nearly three hours at the crease.
Jennings had been badly missed at slip by Stiaan van Zyl on 53 off the luckless George Garton but it wasn't expensive. He added just seven more before edging Carson to slip off a delivery which turned just enough out of the rough.
That left Lancashire 137 for 2, but they then lost four wickets for the addition of just seven runs. Stuart Meaker was rewarded for an excellent spell down the slope when Luke Wells, on his first return to the county where he spent ten seasons, followed one and was caught behind.
Carson's third victim was Steven Croft, who was athletically caught off bat and pad by wicketkeeper Ben Brown diving forward, and it was 151 for five when Vilas was bowled off an inside edge trying to force Atkins through the off side.
Liam Livingstone's first Championship innings of the season lasted just four balls as Aaron Thomason took a juggling catch at short leg to give the irrepressible Carson his fourth wicket and Lancashire had lost 5 for 24 runs in 8.5 overs. Josh Bohannon and Danny Lamb negotiated 23 overs to stumps but their side still trail by 135.
Carson's haul followed his 5 for 85 in Yorkshire's second innings at Hove last week, the visitors winning that match by 48 runs.
Earlier on Friday, Sussex added just 10 runs to their overnight 318 for 7 before they were bowled out with Lamb taking the last three wickets including Carson, bowled via an inside edge, and the bizarre run out of Henry Crocombe, caught short when George Garton struck the ball straight back down the pitch and Lamb stuck out a hand on his follow through, deflecting the ball onto the stumps at the non-striker's end. Garton was last man out, caught at fine leg as Lamb finished with 3 for 59.
Tom Bailey took 3 for 69 before Lancashire's reply was held up by rain just under half an hour before the scheduled lunch break, causing a 40-minute delay.