[11] Christensen made his Fulham debut in the FA Cup third round draw against Norwich City at Carrow Road[12] and came on as a substitute for Steve Sidwell in the 84th minute during the replay at Craven Cottage.

[20] By the end of 2014, Christensen added three more goals, putting his tally to 5, including against Sheffield Wednesday, for which named Man of the Match.

[25][26][27] In the 2015–16 season, Christensen continued to remain in the first team despite facing competitions and resulted being substituted on the bench.

[29] It wasn't until on 26 December 2015 when he returned to the first team, coming on as a second-half substitute, in a 2–0 loss against Derby County.

[31] However, he was sidelined with a hamstring injury after sustaining into the first five minutes to the game against Queens Park Rangers on 13 February 2016.

[36] However, Christensen's first team opportunities was soon limited and was demoted to the club's reserve by the end of the year[37][38] Whilst at Fulham, he went on to make the total of 7 appearances and scoring once in all competitions.

On 27 January 2017, Christensen joined Burton Albion on loan until the end of the season, along with Cauley Woodrow.

[41] Since making his debut, Christensen established himself in the Burton Albion first team and was involved in a squad when they beat Leeds United on 22 April 2017, a win that helped his parent club's more hopes of reaching the play-off and Burton Albion's hopes of staying in the Championship for another season.

[52] On 21 June 2021, Christensen agreed to sign for Belgian First Division A club Zulte Waregem on a two-year contract starting 1 July.

[65] In May 2016, Christensen expressed interest to be called up into the squad for Denmark at the 2016 Olympic Games in Rio de Janeiro.

[69][70] Christensen grew up supporting Premier League side Arsenal, whom he went on a trial early in his career.