Martin started his playing career at Cambridge United before short stints at Welling, Stevenge and Dagenham & Redbridge. Brennan retired from playing in July 2005 and shortly after became Tottenham Hotspur’s Under 18’s goalkeeping coach, a position held for just over 3 years.
After leaving Spurs, Brennan spent 4 years as First Team goalkeeping coach at Wycombe Wanderers and then a further 4 years at Fulham, as goalkeeping scout between 2012 and 2014. During the same period, Brennan was Fulham’s Under 23’s goalkeeping coach. In 2014, Brennan was promoted from the Under 23’s to the First Team. In 2016, Brennan left for Leyton Orient in the same capacity.
With Leyton Orient embroiled in turmoil throughout his stint with the club, Martin took a sabbatical from the First Team football environment for a couple of years, before being convinced to join Boreham Wood as a part of Garrard’s backroom staff in the summer of 2019.