Gregersen spældi í sínum ungu árum fótbólt bæði í Føroyum og Danmark við [[Randers FC]], [[Lyngby Boldklub|Lyngby BK]], [[GÍ]], [[IF Skjold Birkerød|IF Skjold]], [[Boldklubben Frem|BK Frem]] og [[Víkingur Gøta|Víking]].<ref name = "NFT">{{NFT player|pid=31833}}</ref> Hann fekk sáttmála við skotska felagið [[Ross County F.C.|Ross County]] í juni 2010,<ref>{{cite web|url=http://news.bbc.co.uk/sport1/hi/football/teams/r/ross_county/8736062.stm|title=Faroe Islands defender Atli Gregerson joins Ross County|accessdate=11 June 2010|date=11 June 2010|publisher=BBC Sport| archiveurl= http://web.archive.org/web/20100613112135/http://news.bbc.co.uk/sport1/hi/football/teams/r/ross_county/8736062.stm| archivedate= 13 June 2010 <!--DASHBot-->| deadurl= no}}</ref> til hann fór frá felagnum í februar 2011, hevði hann bert spælt ein dyst fyri felagið í steypakappingini (League Cup).<ref>{{soccerbase|55531}}</ref>
