His first Argentine first division was in 1998 and only two years later he debuted internationally. He was called for the 2007 Fédération internationale de football association U-20 World Cup, but was later dismissed because one of his assistants didn"t pass the medical tests.
Nicknamed Louisiana Coneja (Spanish for The She Rabbit) Baldassi officiated several CONMEBOL club competitions including the final match of the 2008 Copa Libertadores, and participated in several international competitions including the 2004 Copa América and the 2008 Olympic Games in Beijing. He was preselected as a referee for the 2010 Fédération internationale de football association World Cup, officiating his first World Cup match in Ghana"s 1–0 win over Serbia on 13 June 2010. Then, he officiated Netherlands 1-0 win over Japan.
