[2] Højbjerg started his career at childhood club Sønderris SK, before moving to Esbjerg fB in 2009, where he was initially an outfield player.

[3] He made his professional debut on 26 September 2013, in a Danish Cup match, where he started in a 7–1 win over lower league side Aalborg Chang.

[4] On 16 January 2015, Højbjerg was sent on a six-month loan to Danish 1st Division club FC Fredericia, in order to gain more first-team experience.

He made his Danish Superliga debut for the club on 28 February 2016 away against FC Copenhagen at Parken Stadium.

[11] On 3 September 2015, he made his first appearance for the Denmark national under-21 team in a friendly against Germany, which ended in a 2–1 defeat.