[1] He made his Brøndby IF debut (in jersey number 31) at the age of 17 as the youngest player ever in the club history when he was brought on for the final five minutes in the 5–1 away defeat against AGF on 13 May 2012.
[4] Frederik Holst ended the 2012–13 season with 24 appearances, in which he was in the starting line-up 17 times, despite the fact that he formally belonged to Brøndby IF's under-19 squad.
[6] Holst had a good season with 30 appearances mostly as right-back, where he managed to push the newly signed Swedish international Michael Almebäck to a seat on the bench.
[7] On 31 July 2014, Holst made his Europa League debut when he was brought in for the final five minutes in the 3–0 away defeat against the Belgium side Club Brugge.
In the first half of the season, he again managed to claim the position as right-back from former Swedish international Almebäck who was shipped off to Esbjerg fB on a one-year loan.
Brøndby IF decided to give him another unseen challenge as they signed Elfsborgs captain and Swedish international Johan Larsson on a four-year contract during the winter transfer window.
[8] The addition of Larsson meant Holst competed with three right-backs as the under-19 and International starlet Svenn Crone was also included in the first team.
Multiple rumours reported that Brøndby IF made a last hour offer to the fellow Superliga club SønderjyskE to add Holst on a loan for the rest of the season.