A youth product of Hvidovre IF, Greko made his senior debut for the first team as an under-19 player against Rishøj Boldklub.
[3] On 8 August 2014, it was announced that Greko would be the new signing of FC Roskilde valid from the new year, as he would become a free agent.
[8] He made his Superliga debut for Brøndby on 27 September 2015, when he came on the pitch in the 74th minute, replacing Magnus Eriksson in the 1–0 victory against Copenhagen.
[15] On 28 May 2022, Lyngby Boldklub announced that Greko's expiring contract would not be extended, making him a free agent after the 2021–22 season.
[19] Before turning professional at Roskilde, Greko studied economics at the University of Copenhagen next to playing football for Hvidovre.