It was throughly discussed what feels like a hundred times. It's a variety of factors, the culture shock being the least important of those. The culture shock assumption is based on the western media depiction of Russia. What is so different about NA except for the language? The important factors are hockey related. A different brand and school of hockey in Russia. Young players who finalize their education in Russia tend to meet expectations or exceed them. Those who make the jump early start learning a different approch to hockey at age 17-18 in NA, while their russian hockey is still raw. They end up not good at any of those hockey schools. There are exemplary exception cases like Provorov who went to NA even earlier at 14 and learned in the US system before going to the CHL. In his case it obviously worked. Have a look at the currently so troubled D development in Russia. Out of russian D-men currently in the NHL only Sergachyov is an exception from the rule. Kulikov and Zadorov both former first rounders develeoped in the CHL and never found that projected potential in the NHL. Zadorov became a somewhat usable DD, but seems to have consistency issues and his CHL numbers on the offence never translated. Kulikov is just mediocre to bad. Orlov(2nd round) - a solid NHLer never played a CHL game. Gavrikov(6th round), Zaytsev, Lyubushkin(both undrafted), developed in Russia and while Zaytsev has at least some resume prior, the other two were not even on the board once and look at them now, they are NHLers. And the defencemen development in Russia is supposed to be bad. With forwards that would be even more obvious.