Mattacchione is a graduate of Father Michael Goetz Secondary School in Mississauga, Ontario. Before he signed for the Lynx he played college soccer for the University of Alabama at Birmingham, where he was the team captain from 1995 till 1997. At Alabama he was named First Team Rookie All-Conference in 1994. He was a 2-Time UAB Team MVP in 1996 and 1997.
In 1999 Mattacchione was drafted by the Toronto Lynx. There he became a fan favourite being named Lynx Defensive Player of the Year in 2002 and leading the team into the playoffs in 2000. In 2004 he was named the new team captain after Marco Reda's departure. In 2006 when Duncan Wilde returned as Head Coach of the Toronto Lynx he appointed him and Theo Zagar as player/assistant coach roles.
During the 2006 season he helped the Lynx to a team-record of a 10 game undefeated streak at home. And also helped the Lynx reach the final of the Open Canada Cup which they lost 2-0 against Ottawa St. Anthony Italia.
After the 2006 season the Lynx dropped two divisions down into the PDL. Making him a free agent after seven seasons with the Lynx. But during his time with the franchise he was ranked in the top five for all-time games and minutes played for the Lynx.
After retiring from soccer, he was appointed the U12 Development Director for the Oakville Soccer Club in 2007.
He teaches a high school careers and gym class at his old high school Father Michael Goetz.