Callum signed a two year deal with Albion in the summer of 2015 after being released by Championship side Birmingham City at the end of last season.
An energetic midfielder who can also play at full back, Callum joined the Blues at the age of seven earning himself a scholarship with the St Andrews club in 2010.
His continued development earned him a first team squad place and his first team debut as a substitute against Sheffield United in the FA Cup in January 2012.
A first professional contract followed and over the next three seasons Callum accumulated over 60 appearances in the Championship gaining valuable experience.
After initially joining Albion on loan in March 2015 he made his debut as a substitute against Accrington Stanley but his full debut three days later was cut short by a hamstring injury that ended his season. Callum showed enough to Brewers boss Jimmy Floyd
Hasselbaink for him to make the Republic of Ireland under 21 international his first summer signing of last summer and Callum will be hoping to re-establish himself as a championship player over the coming campaign.