After just over a year in the Youth ranks at Nene Park, Sam Smith was rewarded with a place in the first team squad in spring 2008. He had joined the club early in 2007 after being spotted playing by ex-Diamonds goalkeeper Kevin Shoemake playing for Corby Town Under 18s, after returning from a short spell with Wrexham as an Under 16, which followed an earlier spell at Nene Park.

Sam made his league debut with a substitute appearance against Cambridge United on 8th April 2008, then went on to make his first League start against Oxford United later that month, and scored his debut goal in the final game of the season against Aldershot. That goal was scored a few days before his 18th birthday, although not quite early enough to shade Lee Tomlin's record for the youngest player to score a league goal for the club.

He was then offered and signed a contract, prior to the start of the 2008/09 season, until the end of the 2010/11 season. After missing the first game of the 2008/09 season, he scored in each of the next three league games, making it a run of four league games in a row where he had joined the game from the bench and scored. He finished the 2008/09 season as joint-top league goalscorer with 8 goals, as well as joint-top overall goal scorer with 9 goals. He made 31 appearances from the bench that season, including his appearance against Kettering Town at Nene Park, where he scored a memorable winning goal.