After starting his career with the local
KPV, Forsell was signed by a near
Veikkausliiga side
VPS in 2009. After struggling to make it in the match squads at Vaasa, he left after only one season, switching to a fellow Veikkausliiga side,
IFK Mariehamn. At Mariehamn, he began appear more regularly and soon attracted the attention of much bigger clubs in and outside of Finland. On 9 August 2012, he was selected as
the player of the month, for July. On 5 August 2012, it was announced that Forsell had signed with
Süper Lig club
Bursaspor for a transfer fee of €500,000. He was handed the number #7 shirt for
the upcoming season. Forsell made his debut for Bursaspor as a substitute on 23 August in a
Europa League qualifying match against
FC Twente. Forsell was selected as the
Ekstraklasa Player of the Month for September 2018. Forsell was the first ever player from
Miedź Legnica to win the award and the first player to win it in his rookie year. On 10 August 2019, Forsell scored one and gave two assists in a 4–0 win against
FC Lahti on his league debut for
HJK as a loan player. After stints with
Korona Kielce and
Stal Mielec, Forsell returned to Finland and signed with
Inter Turku for the 2021 season. On 21 February 2022, Forsell extended his deal with Inter. After leaving Inter at the end of 2023, Forsell remained a free agent until 30 March 2024 before rejoining
Ekstraklasa club Korona Kielce, whom he previously represented in 2020. He made his return to Polish football two days later as a second-half substitute in a 3–1 away loss to
Widzew Łódź. He left the club at the end of June. On 9 July 2024, Forsell signed with Turkish
TFF 1. Lig club
Şanlıurfaspor. He terminated his contract in January due to unpaid salaries. On 18 February 2025, Forsell signed a three-year deal with newly promoted Veikkausliiga club
KTP. ==International career==