Haren is a product of HIK and Nordsjælland. He moved to the latter in 2013.[2] He did not make his debut on the first team as he asked for, and decided not to extend his contract. He wanted to play on senior niveau.[2]
HIK
In the quest for senior football, Haren moved to the third-tier Danish 2nd Division club HIK in July 2016.[3] A month after putting on a strong performance against Danish Superliga club Randers in a Danish Cup match, Haren went on a trial with Randers i November 2016, which went successfully.[4]
Randers
On 8 December 2016 it was confirmed, that Haren at the age of 19, had signed a two-year contract with Randers, starting from the new year.[5]
Haren made his debut for the club on 15 March 2017. He started on the bench, but replaced Marvin Pourié in the 89th minute in a 1–0 victory against SønderjyskE in the cup.[6]
He played his first game in the Superliga on 19 March 2017, where he came on the pitch in the 90th minute, replacing Johnny Thomsen, in a 0–1 defeat against SønderjyskE.[7]
Due to the lack of playing time, Haren left the club after terminating his contract by mutual assent on 11 April 2018.[8] He played 7 official games for the club in total.
After leaving the club, Haren trained the rest of the season at his former club HIK.[9]
Return to HIK
After being released by Randers, Haren returned to HIK.[10]
Helsingør
On 4 December 2018, Helsingør announced the signing of Haren on a contract until the summer 2021, starting from 1 January 2019.[11] Haren left the club in the summer 2021, where his contract expired.[12]
Lucas Haren is the son of the former footballer Piotr Haren, who played for FC Copenhagen. His grandad is Janusz Andrzej Haren, who represented Widzew Łódź and B93.