Puljujarvi was hurt March 4 during a 3-1 loss against IFK; he scored the only goal for Karpat in the second period before the injury.
The 6-foot-3, 203-pound forward has 13 goals, 28 points, a plus-5 rating and 175 shots on goal in 50 games for Karpat in Liiga, Finland's top professional league.
Puljujarvi, 17, also helped lead Finland to the gold medal at the 2016 IIHF World Junior Championship. He was named the best forward and most valuable player of the tournament, and his WJC-best 17 points was the second-most by an under-18 player at the WJC, one behind the 18 points Jaromir Jagr of Czechoslovakia had in 1990.
"Puljujarvi is a big, mobile, skilled, all-around winger who can score and pass," Stubb said. "He's got excellent skating power, plays with determination, wins most battles. He plays with confidence and has all the tools needed to become a star, including the size, skill, speed and will power."