The UFC's return to Northern Ireland is getting a significant reshuffling.

Gunnar Nelson is injured and out of his main event with Dong Hyun Kim at UFC Fight Night 99 on Nov. 19 in Belfast, sources told MMA Fighting's Ariel Helwani. In that fight's place will be a new headliner: a rematch between Gegard Mousasi and Uriah Hall.

The extent of Nelson's injury is unclear at this time. The change has not yet been officially announced by the UFC.

Mousasi (40-6-2) is coming off a second-round TKO of Vitor Belfort at UFC 204 earlier this month. The Dutchman has won three straight and his lone loss since 2014 came against Hall in September 2015 via spinning kick-flying knee TKO. Mousasi, 31, is one of the best middleweights in the world, but is taking a break from trying to move up in the rankings to avenge the loss.

Hall (12-7) has lost two straight, most recently a first-round TKO defeat against Derek Brunson last month. The New York native has not won since beating Mousasi last year. Hall, 32, is an alum of The Ultimate Fighter 17 and had won five of six before this current skid.

UFC Fight Night 99 does not have an official co-main event. On the card, Ian McCall will meet Neil Seery and James Krause takes on Ross Pearson.