Youth and college Vélez began playing soccer at an early age in Puerto Rico with Colegio San Jose, but moved to
Nick Bollettieri's
IMG Soccer Academy when in high school. He then attended
Barry University from 1999 to 2001, playing on the men's soccer team. During his freshman and sophomore years he was named first team All Conference.
Professional Vélez was drafted by the
MetroStars in the
2003 MLS SuperDraft, but decided to sign with the
Seattle Sounders of the
USL First Division instead of playing in
Major League Soccer. While a defender in college, Vélez played as a forward during the 2003 season, before returning to the back line in 2004. He helped the Sounders reach the league finals in 2004. Vélez signed with the
Puerto Rico Islanders in 2005, where he scored 2 goals in 22 games playing as a defender. During the 2006 season, Vélez was instrumental in the Islanders' run to the playoffs and their qualification for the
CONCACAF Champions Cup, the first time in team history they had qualified for either tournament. Vélez was selected to be the Islanders' captain during the CONCACAF Champions Cup qualifiers. During the 2007 season, Vélez scored one goal and added one assist in twenty-seven games. His everyday play as defender was crucial to the Islanders advancing for the first time in team history to the USL Semi-Finals. Velez led the Islanders in matches and minutes played. In July 2007, the
California Cougars of
Major Indoor Soccer League drafted Vélez in the sixth round (49th overall) of the league's supplemental draft., but he never played for the team. Vélez transferred from the Puerto Rico Islanders to
Toronto FC in 2008, and in doing so became the first native Puerto Rican to participate in MLS. He made his MLS debut on 29 March 2008 in a 2–0 defeat to
Columbus Crew. In his first season in Major League Soccer, Vélez started all the games in which he participated.
Toronto FC released Marco on August 13, 2009 and returned to his former club
Puerto Rico Islanders. Vélez left Toronto with 38 appearances, 31 of those as a starter. The defender compiled 2,753 minutes and finished his time with the club with two goals, four cautions, and two ejections. In 2010, he re-signed with the
Islanders.
International Vélez made his debut for the
Puerto Rico national football team in 2004, and was named captain of the team by coach
Colin Clarke in 2008. He scored his first and only goal at the
2012 Caribbean Cup against
Dominican Republic.
Coaching career While playing his last season in the Puerto Rico Islanders, he also served as assistant coach. In 2013 he assisted
Jeaustin Campos with the
Puerto Rico U-15 national football team. In 2015 he coached
Bayamón FC. In 2016 he was appointed assistant coach for
Puerto Rico FC. He served as assistant coach until early 2017 when he took charge as interim head coach. After finishing the season with Puerto Rico FC, the team announced that it wasn't coming back for the 2018 season. In January 2018, he returned as head coach for
Bayamón FC. In June 2018, he took the role of assistant coach of the Puerto Rico national football team after former Toronto FC teammate
Amado Guevara was appointed as head coach. In December 2018,
Amado Guevara confirmed that Marco Vélez will coach the
Puerto Rico national under-17 football team during 2019 World Cup Qualification. ==Honors==