Thacker finished third in the voting behind the winner, Bath Rugby centre Ollie Devote, and runner-up Luke Cowan-Dickie, the Exeter Chiefs hooker.
The LV=Breakthrough Player Award aims to recognise the next generation of young players competing in the LV=Cup, a competition renowned for developing future stars.
England internationals Jonny May (Gloucester) and Jack Nowell (Exeter) are previous winners of the award.
Claire Jeromson, head of sponsorship at LV=, said: “It is incredibly exciting to see so many talented young players get given the chance to breakthrough for their clubs in the LV=Cup.”
As part of Devoto’s prize, a grassroots club of his choice will receive a £1,000 donation from competition sponsors LV=.