At the end of the 1959 season Watson decided on a switch of codes after wanting to forge a career in rugby league. After viewing an advertisement listed in the Sporting Chronicle by St. Helens offering trials for 'top class Rugby Union forwards', Watson replied offering his services to the club and outlining his statistics and credentials he had accomplished in rugby union. St. Helens quickly replied and a trial was organised for 2 August after which Watson was signed to a six-game contract worth £1,500.