Bristol City A left-sided
defender who also has played the left side of the
midfield, Brennan grew up in
Newmarket, Ontario, and started playing with Bristol City youth team in 1994 and made his professional debut in 1996 with
Bristol City against cross town rivals Bristol Rovers in the
Football League First Division. In 5 years Brennan had five managers including Russell Osman, Benny Lennartsson, Joe Jordan, John Ward and Tony Pulis. In 64 first-team appearances for City over five seasons, Brennan scored three goals. Brennan started his career in the Bristol City youth team and worked his way into the first team before being sold to Nottingham Forest.
Nottingham Forest Brennan joined
Nottingham Forest for £1.5 million in October 1999 and was bought by ex-
England captain
David Platt. Brennan was the first Canadian-born player to be sold over the 1 million pound mark. In 146 games played with Forest over four seasons under David Platt and
Paul Hart, Brennan scored just once, in a 4–0 victory against
Norwich City, He also became the first Canadian to score for Toronto FC, registering a goal off a free kick against the
Columbus Crew on 26 May 2007. This goal subsequently became a Sierra Mist Goal of the Week. Brennan went on to play 27 games, all of them starts, for Toronto FC, the most of any player. He earned a reputation as Toronto's "Iron Man," as he managed to play many of his games despite a rib injury, and looked as though he would go on to play every match of the season. Unfortunately, a knee injury prevented Brennan from achieving this feat. Brennan retained the captaincy for the 2008 season, and nearly managed to score in his team's opening match. Brennan has since added goals in 2008 against Chivas USA in Carson, California and to open the 2009 season at Kansas City, off pass from newly acquired Canadian international teammate
Dwayne De Rosario. Brennan also made an appearance during the 2008 MLS All-Star game in his home stadium, BMO Field. The MLS All-Stars won the game 3–2 against
West Ham United. On 6 April 2010 Brennan retired as player to become the assistant general manager for Toronto FC. ==International career==