After Bury's relegation, Shannon replaced Stan Mortensen as manager of Blackpool, with whom he had instant success, finishing as runners-up to Huddersfield Town and winning promotion back to the First Division. This was achieved without the services of the club's star player, Tony Green, who sat out the entire 1969–70 season due to injury. In 1970–71, however, Blackpool finished bottom and were relegated to the league's second tier once again. Shannon had left his position only two months into the season and after only seventeen months in charge. He was replaced, in a caretaker role, by Jimmy Meadows; his permanent successor at Bloomfield Road was Bob Stokoe.