Rob Newton and James Middlebrook dug Northamptonshire out of potential trouble at the Ageas Bowl with an unbroken stand of 72 after hosts Hampshire had threatened to get on top.
Only 48 overs were possible because of morning rain, with the visitors reaching 170-5 after Hampshire captain Jimmy Adams decided to field first on a green wicket which helped his seamers early on.
Niall O’Brien was first out at 20 in the sixth over, chasing an out-swinger from James Tomlinson and giving wicketkeeper Michael Bates an easy catch.
From that moment Northants went through a difficult period slumping to 98-5 before Newton and Middlebrook began the rescue with a defiant late partnership.
Experienced second-wicket pair of David Sales and Stephen Peters took the score to 59 before David Balcombe, another bowler for whom the conditions were ideal, bowled Sales.
Peters was third out at 87, held at slip by Liam Dawson off Chris Wood at the start of a spell in which three wickets fell in four overs.
Peters had held up Hampshire with a brave 47 from 74 balls but in the next over Alex Wakely followed him back to the dressing room after edging Balcombe to Adams in the slips.
Tomlinson came back to remove Andrew Hall to another edge into the slips, Adams again the catcher, and suddenly Northants were struggling.
Then Newton and Middlebrook came together and although they had some uneasy moments, managed to survive until stumps n the first day of the Championship clash.
Newton struck a six off Sean Ervine and six fours in his unbeaten 46 while the circumspect Middlebrook was 26 not out, their sixth wicket stand gleaned from 20 overs.
Tomlinson took 2-27 and Balcombe, rediscovering his early-season form, had taken 2-16 from 12 accurate and testing overs.
Hampshire, in second place and seeking an instant return to Division One, left out the injured Dimitri Mascarenhas and batsman Bilal Shafayat from their squad to accommodate pace bowler Wood.