Sam started off his career at Nottingham Forest as a trainee, however was released without making a first team appearance following the club's snub in order to offer him a professional contract.
Shortly after Mullarkey joined hometown side Lincoln United of the Northern Premier League, but departed the club in 2007.
His career was kick started when he joined Grantham Town in 2007, following previous Lincoln United manager John Wilkinson.
Mullarkey netted 19 times for the Grantham in 53 appearances, however he sustained injuries in a car accident during the pre-season, delaying his debut.
Mullarkey joined Lincoln City, a team he supported as a boy, towards the end of the 2007–08 season after impressing in a number of pre-season games.