Listed at 6-foot-3 and 201 pounds, Ristolainen is regarded as a hard-hitting player who also possesses a heavy shot. He had three goals and 15 points in 52 games in his first full season playing for Finland's TPS last season. Ristolainen has also combined for two goals and nine points in 13 games in each of the past two World Junior Championships.
Goran Stubb, the NHL's director of European scouting, described Ristolainen as one of the best young defencemen in Europe in his age group.
The Sabres follow up with another first-round pick, 16th overall, acquired in a trade that sent captain Jason Pominville to Minnesota in April.