After a strong second half to the 2009–10 season where he earned a regular roster spot on Brynäs IF, Järnkrok went from 21st among European Skaters in the midterm rankings to 4th among European Skaters in the Central Scouting final rankings for the 2010 NHL Entry Draft.[3] He was drafted in the second round, 51st overall, of the 2010 NHL Entry Draft by the Detroit Red Wings.[4]
Calle Järnkrok in 2012
Twenty-eight games into the 2010–11 season, Järnkrok led all junior players in points with eight goals and nine assists and was selected to be the second of four Elitserien Rookie of the Year candidates of the season.[5]
During the 2014–15 season, in his first full NHL season, Järnkrok recorded 7 goals and 11 assists in 74 games. He posted two goals and seven assists in his first 12 NHL games, including five points in the first five contests of his NHL career, the second-longest point streak by a Predators player in the first games of their NHL career, behind Marek Židlický's six games from 9–23 October 2003. On 17 July 2015, the Predators re-signed Järnkrok to a one-year contract.[9] On 26 July 2016, Järnkrok was again re-signed by the Nashville Predators to a six-year, $12 million contract.[10]
Having played his eighth season with the Predators following the pandemic delayed 2020–21 campaign, Järnkrok was left exposed by Nashville and selected at the 2021 NHL Expansion Draft by the Seattle Kraken on 21 July 2021.[11] On 16 March 2022, five days before the trade deadline, Järnkrok was traded by the Kraken to the Calgary Flames for the Florida Panthers' 2022 second round draft pick, the Calgary Flames' 2023 third round draft pick and 2024 seventh round draft picks.[12] Järnkrok played in 12 playoff games with the Flames, scoring one goal and three assists.[4] At the end of the season, he became an unrestricted free agent.[13]
^Nilsson, Johan (13 January 2010). "Brynäs och Ironhook". Hockeysverige.se (in Swedish). Archived from the original on 22 May 2010. Retrieved 8 May 2010.
^Järnkrok's nickname is a direct translation of his last name into English.