Holtby started playing rugby at the age of ten for his local club in Beverley. He went on to play for Hull Ionians and Loughborough University before joining the academy at Leicester Tigers. He played premiership rugby for Leicester Tigers in the 2002-2003, 2003-2004 and 2004-2005 seasons, second tier rugby for Earth Titans (Rotherham) in the 2005-2006 season and premiership rugby for Leeds in the 2006-2007 and 2007-2008 seasons.
After he left Leeds he played for Stourbridge before joining Birmingham & Solihull.
Holtby attended Hull Grammar School where he also took part in athletics and football and he has represented Great Britain in athletics. He studied Engineering and Sports Technology at Loughborough University.
He was a fitness coach on the Gladiators television show.