The 18-year-old Moscow, Russia native played 63 games with the London Knights of the Ontario Hockey League this past season, scoring six goals and adding 19 assists for 25 points. He also had 54 penalty minutes and was rated a plus-33.
At 6'5", 220 lbs, the Sabres hope Zadorov can be a big, physical presence on the blue line.
"Watching Nikita throughout training camp and the preseason has solidified our opinion that he will be a good, young hockey player for our organization going forward," said Darcy Regier. "He has exceptional presence on the ice and we look forward to seeing him continue to develop as a player."