Haines’ hundred, the third of his first-class career, came off 177 balls. It helped Sussex to recover to 291 for 9 by the close - after a grim morning when their decision to bat first appeared ill advised.
Lancashire were still dominant when they reduced Sussex to 127 for six but Haines and Ollie Robinson had come within one run of doubling that score when Robinson was caught behind off Saqib Mahmood for 59. Having batted for 357 minutes and hit 20 fours, Haines was finally dismissed when his tired swish edged a catch to Alex Davies and that wicket gave Tom Bailey his third success of the day.
Haines said: "It was a tough day, we had to graft for our runs and I’m chuffed to bits with that score. They gave us nothing in that first spell. I was lucky when that chance went down but we’re a club that really needs to stick together and show fight. I think we’ve done that today.
"Ollie Robinson helped me but so did Delray. You get into trouble if you go searching on 99 and I just had to wait for the bad ball. The career-best wasn’t on my mind but then I heard a clap on 125 and I thought ‘oh it’s that one’.
"I’ve been practising so hard over the last few months and I feel like a different player. I’m not so lazy in training and it’s been a real attitude switch. It’s come from within. I wasn’t enjoying my cricket in 2019 and it was quite demoralising, so I went back to a few coaches I’d had when I was younger and they told me I had all the ability but it was a mental game."
The first session of play was controlled by Dane Vilas’s attack. Makeshift opener Aaron Thomason was castled for three when playing no shot at Mahmood and Stiaan van Zyl’s first innings for Sussex since 2019 ended when he was leg before wicket to Tom Bailey for a seven-ball duck.
Tom Clark also perished for nought when he hooked Luke Wood’s fifth ball of the morning straight to Danny Lamb at long leg and Bailey returned to have Ben Brown caught at slip by Steven Croft for four. But the visitors’ spirits were raised in the morning’s final over when Haines, having been hit on the hand by Lamb took 12 runs off the next four deliveries, thereby reaching his fifty off 94 balls.
The opener batted had added 66 with Delray Rawlins when his partner was leg before wicket for 18 when not attempting a shot to a ball from Wood. George Garton was caught by Keaton Jennings off Lamb for 10 but Robinson adopted a more aggressive approach and that rubbed off on Haines. Having been dropped twice at second slip by Croft during the morning, the Sussex opener was put down again by Jennings at first slip off Josh Bohannon when he had made 121.
Robinson eventually fell to the new ball and Haines was dismissed five overs later. The pair’s 126-run stand set a new seventh-wicket for Sussex against Lancashire. Bailey was the most successful bowler with three for 41 but Wood, Mahmood and Lamb also took two wickets.