Ristolainen is used to getting started quickly. He made his debut with TPS Turku in Finland's Liiga at age 16 in 2010-11 and later jumped right into the lineup for the Buffalo Sabres at 18 for 2013-14 NHL season.
Ristolainen, selected by the Sabres with No. 13 pick in the 2013 NHL Draft, made his League debut Oct. 2, 2013, against the Detroit Red Wings and scored his first NHL goal Oct. 25, 2013, against the Florida Panthers. He had four points in 34 games for Buffalo in 2013-14 and played in the 2014 World Junior Championship, where he scored in overtime against Sweden to win the gold medal for Finland. Ristolainen had three goals in five games during the tournament.