He was appointed in December 2024 after predecessor Jon Brady – now in charge at FA Cup giant-killers Port Vale – resigned and guided them to 19th place last season.
The 43-year-old moved to Sixfields following a spell as a first-team coach at West Ham, having previously managed Leyton Orient and Notts County.
They failed to win any of their first four games this season, before four victories in the next five lifted them to mid-table.
Nolan’s side beat AFC Wimbledon 3-1 on 19 December but ended 2025 with back-to-back defeats at the start of a run of nine games without a victory.
They eventually beat Stevenage 3-1 on 7 February but have not won in the league since then and last week were knocked out of the EFL Trophy at the semi-final stage, losing 2-1 at Luton Town.
Speaking following Saturday’s game, Nolan insisted he was ready for a “dogfight” to try and preserve Northampton’s third-tier status.
“We’ve got to scrap our way out of it – that’s the only way you get out of these situations,” he told BBC Radio Northampton.
“The relentless schedule has been ridiculous, it has hurt us, affected us but it’s now up to us to fight our way out of it.”
Northampton have 10 games left this season, the first at home to Burton Albion on Saturday.
Acting boss Calderwood led them promotion from League Two in 2006 and later had spells in charge of Nottingham Forest, Hibernian and Cambridge United before returning to the club as technical director in January 2025.
Sampson was manager from 2009 to 2011, having previously played almost 450 games for the club as a central defender.
