 On September 15, 2004, he was signed as a free agent by the San Jose Sharks.Armstrong was immediately sent down to the Cleveland Barons for two seasons, scoring a combined 12 goals.Armstrong spent the next three years with new Sharks affiliate, the Worcester Sharks before he made his NHL debut in the 2008-09 season with San Jose on November 29, 2008 in a 3-2 win over the Phoenix Coyotes playing on a line with Jeremy Roenick and Jody Shelley.