After a successful 2007–08 season completing 4 goals in 25 games, Díaz was transferred to Boca Juniors, following his coach Carlos Ischia footsteps, who also left the club for Buenos Aires-based team.

After being appointed Boca, Díaz made his official debut in a 4–0 Copa Sudamericana win over last Copa Libertadores champions LDU Quito on 23 September 2008 as a 83rd minute substitution. At La Bombonera team he won the Torneo Apertura (being that his first professional title), which he failed to play it, because he was under the "shadow" of Juan Román Riquelme as the team's playmaker into Ischia's scheme.

Díaz made his Chilean Primera División début on 27 July 2009, in a 2–0 win over Deportes La Serena at San Carlos de Apoquindo. He scored his first two goals for the club on 23 August, both in a single match against Cobreloa, in where Católica won 2–0 thanks to the goals of Díaz. One month later, he scored his first hat-trick in his career in Católica's 7-0 thrashing of Curicó Unido, should be noted that one of his three goals was olympic. Díaz also scored in the following week against Audax Italiano, match that was won 4–0 by Católica. In that season, Damián was fully consolidated in the position of playmaker at the scheme of Católica's coach, Marco Antonio Figueroa. He was also paired in attack with Juan José Morales and Milovan Mirosevic. The team reached the final against Colo-Colo, but lost 6–4 on aggregate. Following his debut season in the Chilean Primera División, Díaz emerged as one of the league's finest playmakers.

On 11 June 2010, Colón de Santa Fe signed him for one year, on loan from Boca Juniors.

On 11 June 2011, Diaz signed with the Ecuadorian Barcelona. His debut came in July 23, 2011 in a 2–2 away draw against Espoli. In just his third match for Barcelona, Diaz scored his first goal for the club, the only winning goal, in a home win against CD Olmedo on August 8. His next goal came in a 3–0 home win against Imbabura FC. Diaz' 3rd goal for Barcelona was on September 25, in a 2–1 home win over Deportivo Cuenca. He then scored a double on October 16, in a thrilling 3–0 away win over Independiente Jose Teran. His final goal of the season came in Ecuador's Super Clasico, in a 2–0 home win over Emelec on November 19. He finished the league having played 20 matches, scoring 6 goals and assisted 3 more.

In 2012 Barcelona signed Diaz to a 4-year contract, when Diaz was being observed by clubs like Cruz Azul and Fluminense . Diaz has helped Barcelona in their road to win Barcelona 14th Ecuadorian Serie A title. Damian Diaz' first match for the 2012 season was a 3–1 home win over Deportivo Cuenca on February 5. His first goal of the season came several months later, but was an absolute GEM, an over-head goal from a cross nearly 40 yards out, was the second goal in a thrilling 3-0 home win over Tecnico Universitario. On July 8, Damian Diaz, though in a losing 1–0 match against Deportivo Cuenca, it ultimately led to Barcelona ending up finalists for the 2012 League championship final match.

His first match of the season was a 1–1 away draw against Deportivo Quevedo on January 26. His first goal of the season was on Barcelona's Copa Libertadores 2013 debut, a 2–2 away draw against Nacional of Uruguay, he scored the opening goal from long-range. Next he scored in a historically humiliating defeat to Independiente Jose Teran, scoring the 2–1 lead for Barcelona, then Independiente turn the game around in the final 10 minutes, defeating Barcelona 5–2. On March 6, Diaz scored against the Mexican club Toluca in a Copa Libertadores match, drawing 1–1. On April 28, Damian scored twice against Ecuadorian giants LDU Quito, in a triumphant 3–0 home win.