Matt Machan scored a blistering 100-ball 135 but Sussex rather squandered his good work on the first day of their LV= County Championship Division One meeting with Worcestershire at the BrightonandHoveJobs.com County Ground.
Machan, playing in his first Championship game since last June, pulverised Worcestershire's seam attack, reaching his third first-class hundred with his fourth six and also hitting 18 boundaries.
The Scotland international added 145 for the second wicket with Ed Joyce, who scored 49, but Sussex were never the same after the latter drove loosely at Jack Shantry and was caught at second slip.
From 161 for two they lost wickets regularly and, despite a third successive half-century by Luke Wright, failed to claim maximum batting bonus points having been dismissed for 345.
“I play better when I’m aggressive and go for my shots and it is something I have worked on," Machan said after the day's play had concluded. "I’m trying to take my game forward in red-ball cricket by playing more positively.
"I only knew I was playing this morning so I decided to be aggressive from the start and once I’d got myself in I really enjoyed myself.”
Machan, only playing because Chris Nash and Mike Yardy were ruled out through injury and illness respectively, arrived in the sixth over when opener Luke Wells was dismissed for nine, well caught at third slip driving away from his body.
His first scoring shot was a boundary sliced over the slips but he soon settled down to play aggressively on all sides of the wicket, feasting on any width and pulling confidently in front of square when the bowlers dropped short.
His first 50 came off just 27 balls and included two leg-side sixes, the first of which sailed out of the ground.
Worcestershire introduced Sri Lanka off-spinner Sachithra Senanayake in the 22nd over to try and bring some control, but Machan bludgeoned his fourth ball over midwicket for six and at one stage looked on course for a century before lunch, which Sussex reached prosperously placed on 153 for one.
Machan struck Charlie Morris for two fours in three balls and brought up his second Championship hundred with his fourth six, off Shantry.
However, by then he had lost Joyce, well held at second slip driving at Shantry, having been dropped in the previous over.
Morris surprised Craig Cachopa with a bouncer which took the shoulder of the bat before a relieved Worcestershire finally snared Machan in the 45th over, when his mis-timed flick off Shantry was held at deep midwicket.
Wright played attractively for his 51 from 67 balls and hit eight boundaries, but the solid partnerships Sussex needed from their middle and lower orders never materialised.
Both Wright and Ben Brown got out to loose shots before Senanayake picked up two wickets in two balls.
It was left to Ajmal Shahzad to ensure Sussex did not totally squander such a good start.
He finished undefeated on 45 but was left high and dry when last man Matthew Hobden became Gareth Andrew's third victim with a fourth batting point in sight.
The odd ball bounced sharply and there was some slow turn for Senanayake, but the pitch played well enough and, in 15 overs, openers Daryl Mitchell and Richard Oliver took Worcestershire to 45 for nought at stumps.
Worcestershire director of cricket Steve Rhodes said: “When a batsman hits the ball as sweetly as Matt did today it can be difficult to bowl at. It was a special innings because he climbed into some really good balls. We were a bit shocked by the onslaught.
“I was pleased we managed to drag it back a bit after he chipped one up. It’s a good cricket wicket. There is some pace there but you can score quickly and we did well in the end to restrict them to 345 and then get through 15 overs before the close without losing a wicket.”