[3] After a stint in a youth sector of FC Honka, Källman made his senior debut for EIF in the third-tier Kakkonen on 3 May 2014, at the age of 15.

Next 2021 Veikkausliiga season, Källman scored 14 goals and was the league's joint top scorer with Ariel Ngueukam.

[11] On 2 July 2022, Källman moved to Polish side Cracovia on a free transfer, signing a three-year contract with the club.

[17] At the turn of November, Källman scored two braces in two consecutive Ekstraklasa victories, against Motor Lublin[18] and Lechia Gdansk,[19] respectively.

Subsequently, Polish media reported of a notable offer previously made by an unnamed Turkish club, which Cracovia had rejected.