Date of birth
A versatile operator, Mason is in his third year as a professional after graduating through the Rotherham United Academy.
He signed a contract extension at the end of the 2016/17 season to remain at AESSEAL New York Stadium.
During 2015/16 he enjoyed a loan spell at Sheffield FC, and was on the bench for the Millers for the FA Cup third round tie against Leeds United at Elland Road.
He made his professional debut for the Millers in a League Cup tie against Morecambe in 2016, and was a regular in the matchday squad throughout the season.