Marth broke into the senior setup at National Soccer League club Sunshine George Cross FC. He spent four seasons with the Western-suburbs based club before moving to nearby fellow NSL club Melbourne Knights FC in 1989. In the 1990-91 season, he won the Minor Premiership with the Knights but lost the Grand Final by penalty shootout to bitter rivals South Melbourne FC. Marth scored the only goal for Knights, at the 26th minute, but the final score was 1-1. With Melbourne Croatia, Marth would then collect two more Minor Premierships but lose two more Grand Finals, both to Adelaide City.