Northamptonshire 242 for 6 (Vasconcelos 83, Cobb 62) trail Sussex 422 (Jordan 166, Brown 156) by 180 runs
A day that began with the Northamptonshire captain sidelined by a freakish concussion injury suffered nowhere near the field of play ended with another of their number possibly ruled out of the game after a more conventional blow to the head.
Luke Wood, the left-arm pace bowler on loan from Nottinghamshire, ducked into a short, quick ball from Chris Jordan at the start of the final scheduled over and reeled away from the impact, which looked to be on the side of the the helmet.
He stayed on his feet and seemed prepared to continue with new headgear but after an examination by the Northamptonshire physio it was deemed sensible not to expose him to anything else with close of play so near and he was led from the field.
"He is a bit groggy and we are hoping he will be okay but it was a pretty hard blow and he will be assessed for concussion in the morning," the county's assistant coach, Phil Rowe, said.
Alex Wakely's absence was in altogether more freakish circumstances, the captain having left the ground in fine fettle on Monday evening only to walk into a low beam in his house. He drove to the ground to prepare for the second day as normal, but began throwing up in the dressing room, a classic symptom of delayed concussion.
He went to hospital for assessment later but doctors are confident he has done no serious damage to himself and he was allowed home, although he will take no further part in this match. Josh Cobb has replaced him as a concussion substitute under ECB rules, even though his injury was not incurred during play.
Cobb, who had made way for Adam Rossington in the original XI, took his unexpected chance well enough, sharing a stand of 137 for the second wicket with Ricardo Vasconcelos, but might have made more of it, which could also be said of his partner.
Vasconcelos, a South African with a handy Portuguese passport among his possessions, is a decent young player, well organised and with some shots in his armoury, and already with a couple of centuries to his name this season.
He might well have had another here had the excitement not gone to his head with the last ball before tea when, for reasons he could not explain even himself given the way he threw his head back at his foolishness, other than perhaps the couple of lovely cover drives for four that had taken him to 86 in the same over, he went for an ambitious sweep against Danny Briggs and was leg before.
"I felt like I was playing well and I know I should have blocked it really," he said afterwards. "It was a shame because the session had gone well for us up to that point."
Sussex would argue that he was lucky to be there are all, having survived a fairly routine chance to second slip off David Wiese on 7 just before lunch, but a hundred looked his for the taking nonetheless.
Cobb had some way further to go before he could start thinking along similar lines but will feel he could have made more than 63. Facing the first delivery of a new spell from Abidine Sakande after tea, the right-hander was tempted into a hook, the ball going a long way up but finding the safe hands of Mir Hamza at long leg when it came down.
Hamza, the Pakistan left-arm seamer, was tidy and testing every time he bowled, claiming the wickets of Ben Curran and South Africa Test batsman Temba Bavuma, both caught at slip. Wickets for Jordan and the legspin of Luke Wells late on left Northants 180 adrift at the close.
It was the Vasconcelos dismissal that created an opportunity for Sussex, who took maximum batting points despite Jordan and Ben Brown being unable to add substantially to their 302-run partnership and will believe they can press on from here to claim a second win of the season.