Life turned for the worse for Calum Haggett ahead of the 2010 Under-19 World Cup when he discovered that he was suffering from a potentially fatal heart disease - one which needed an emergency open heart surgery. As such, he wasn't considered for the Under-19 England squad and his health condition had an impact on his career with Somerset.

Having made a full recovery, Hagget struggled for opportunities in Taunton before leaving the club at the end of the 2011 English domestic season. Kent was a better place for Haggett as he picked up the pieces of his career and started to show consistent improvement with both ball as well as bat. Having signed a contract in 2013, he finished the season with a batting average of more than 35 and also scalped 26 wickets. This led him to signing a fresh contract ahead of the 2014 season.