"I've sat down with a few boys going through the system. I'm a strong believer that, if you're good enough, you should be there. The weight will come. I don't think guys at 14 should be smashing the gym.'
"There's a lot of pressure for youngsters to be bigger, stronger, faster,' he said. 'There's probably more focus on that than their core skills. Passing, tackling, stuff like that.
"There is a lot of pressure and I think it's directed at the wrong things. When you're 18, 19, 20 is when your major growth should occur. Not at 16."
Thacker, who has been a shining light for Bristol this season, stands at 176cm tall and weighs 93kg. In comparison, All Blacks hooker Dane Coles stands at 184cm and weighs 109kg.
Thacker told the Mail on Sunday he got into the gym a lot when he was younger, "trying to hit every muscle group I could to try to put weight on".
"I put on as much weight as I could put on — to the point I wasn't as able to play the game I wanted to play."