In September 2003, Brubaker began skating with Mariel Miller, with whom he competed on the junior level. They won bronze medals at the 2004–05 ISU Junior Grand Prix Final and the 2005–06 ISU Junior Grand Prix Final. They won the junior title at the 2005 U.S. Championships. While originally intending to compete at the senior level at the 2006 U.S. Championships, Miller & Brubaker announced their split in December 2005 due to a lack of height difference that could lead to injury. They were coached by Dalilah Sappenfield and Tom Zakrajsek.