The UFC’s debut event in Denmark needs a new fighter for the co-main event.

Thiago Alves (23-14 MMA, 15-11 UFC) has been forced to withdraw from a planned meeting with Gunnar Nelson (17-4-1 MMA, 8-4 UFC) at this month’s UFC on ESPN+ 18 event MMA Junkie today learned from a person familiar with the matter but not authorized to discuss it publicly.

UFC officials are currently seeking a replacement opponent to face Nelson at the Sept. 28 event, which takes place at Royal Arena in Copenhagen and streams live on ESPN+.

Injury is to blame for Alves’ withdrawal, though specifics of his condition were not immediately available and a timetable for his return was not established.

Icelandic grappling standout Nelson is looking to rebound from a split-decision loss to Leon Edwards at UFC on ESPN+ 6 in March in an outcome that saw him fall to 4-4 in his past eight fights, after opening his career undefeated through his first 14 pro contests.

The UFC on ESPN+ 18 lineup currently includes:

MAIN CARD (ESPN+, 2 p.m. ET)

Jack Hermansson vs. Jared Cannonier

Gunnar Nelson vs. opponent TBA

Michal Oleksiejczuk vs. Ovince Saint Preux

Alen Amedovski vs. John Phillips

Ion Cutelaba vs. Khalil Rountree

Macy Chiasson vs. Lina Lansberg

PRELIMINARY CARD (ESPN+, 11 a.m. ET)

Alessio Di Chirico vs. Peter Sobotta

Nicolas Dalby vs. Alex Oliveira

Danilo Belluardo vs. Mark Madsen

Siyar Bahadurzada vs. Ismail Naurdiev

Marc Diakiese vs. Lando Vannata

Nohelin Hernandez vs. Jack Shore

Mike Davis vs. Danny Henry