Italian American Mario Longo played for Norwich's Under 19s in their 2-0 victory over Millwall on 6th March 1999. He was previously with Italian side Napoli's youth side for two years, after impressing in a trial with them in August 1996. Mario has since had trials with Charlton, impressing for their Reserves against Swindon on March 24th 1999. The South London Press stated that Mario had "a solid game."

The Pink Un reported on 13th November 1999 that Mario had signed for Eastern Counties League side Wroxham whilst currently on trial once again with the Canaries. The Pink UN reported that Mario had played for the USA's youth side. He made his debut for Wroxham in the Jewson League Cup on 9th November 1999.

On April 1st 2000, he signed for the Nike Project 40 side in the USA's A-League but on 8th May 2000, he joined MLS side Columbus Crew as part of the MLS lottery system. The 20 year old from North Carolina was described as big, strong and technically gifted. Mario returned to North Carolina in the summer of 2002 to join the Carolina Dynamo, who play in the A-League and name Bob Rosario as one of their former coaches.

Longo returned to Europe in the autumn of 2002, signing for Irish side Waterford United but he has since left them. After a spell with the Syracuse Salty Dogs, he is currently with the Puerto Rico Islanders.