De Guzman was discovered by representatives of Olympique Marseille while playing for the North Scarborough youth soccer club in Toronto.

De Guzman was heavily criticized for his inconsistent performances as a designated player in the 2010 season making 36 appearances in all competitions.

Much doubt was left over the future of de Guzman and Toronto on November 23 when the club failed to protect him for the 2010 MLS Expansion Draft, meaning Vancouver Whitecaps FC or Portland Timbers could select him if they were willing to take on a Designated Players Salary.

[13] On January 5, 2011, de Guzman revealed that he would be undergoing knee surgery to repair a torn meniscus which might have plagued his performance for the last quarter of the season.

[15] Ten days before the new season kicked off it was revealed that de Guzman would miss this first game against Vancouver and potentially a few more, due to Winter not wanting to aggravate the recent successful surgery.

De Guzman scored his first goal for Toronto in CONCACAF Champions League play against Tauro FC August 18, 2011, the game ended in a 2–0 away victory.

[17] De Guzman made his debut for Dallas against San Jose Earthquakes on July 18, the game ended in a 2–1 away defeat.

[18] De Guzman scored his only goal for Dallas on September 15 against Vancouver, a left footed volley more than 20 yards out six minutes into second half stoppage time.

[23] Following the 2013 CONCACAF Gold Cup in late July, de Guzman signed for Skoda Xanthi in the Superleague Greece.

[30] De Guzman played at the 2001 FIFA World Youth Championship in Argentina, alongside Atiba Hutchinson and Mike Klukowski among others.

[32] In Canada's opening match of the 2007 CONCACAF Gold Cup, de Guzman scored twice to help defeat Costa Rica 2–1.

[33] De Guzman was also chosen in the 23-man roster for the 2009 CONCACAF Gold Cup, Canada won group A with seven points before being knocked out by Honduras in the quarter finals.

[34] De Guzman earned his fiftieth cap for Canada's senior men's team on October 7, 2011, in a dominating 7–0 victory over Saint Lucia in a 2014 FIFA World Cup qualification match at Beausejour Stadium.

[38] On December 21, 2017, de Guzman was appointed general manager of the Ottawa Fury, alongside new head coach Nikola Popovic.

[39] He held the role until the Fury ceased operations at the end of 2019, following not receiving sanctioning to play in the US-based USL Championship.