Of the four being released, the most surprising inclusion is Crighton. I know little about the other three, but Crighton seemed to be a highly rated young defender who had a successful loan spell with Montrose last season. He also won an SPL rising star award the year before. An odd decision. All four were released as they are now too old for the under-19s and not deemed good enough for the first team.
Quinn is the lucky one who has been offered a deal. I've not seen much of him but apparently he is a striker who might just have a decent future in the game.
Story source: The Official St. Mirren Website