Career
Undrafted, Keränen first played as a youth in his native Finland with Tappara before moving to Ilves as a 17-year-old. Keränen made his professional debut in the Master of Science-liiga with Ilves at the conclusion of the 2009-2010 season. After his fifth season with Ilves, in which he led the team in scoring with 52 points in as many games, Keränen initially signed as a free agent on a one-year contract with rival Finnish Liiga club, HIFK on April 30, 2014.
A little over a month later, Keränen exercised his National Hockey League out clause to leave HIFK and sign his first National Hockey League contract on a one-year, two-way deal with the Minnesota Wild on June 5, 2014.
In the following 2015-2016 season, Keränen returned to the Iowa Wild for a second season. He was leading Iowa in goals when on November 17, 2015, he received his first recall to the Wild.
Making his National Hockey League debut later that night against the Pittsburgh Penguins. He was prompty returned to the AHL and on February 29, 2016, he was dealt by the Minnesota Wild, executing a minor league trade deadline deal, to the Ottawa Senators in return for defenseman Conor Allen.