Newcastle defender Dan Burn is facing months on the sidelines with an injury to his spine.
The 31-year-old hurt his back after landing awkwardly following an aerial challenge during Sunday's 1-0 Premier League win over Arsenal and could be out for around two months.
"Dan will be out for some time, I think, so it’s another long-term problem," said Newcastle manager Eddie Howe ahead of his side's Champions League trip to Borussia Dortmund.
"A couple of months is sort of a speculative number for us. He landed on his spine. I think he's got a problem with the base of his spine, so a huge blow.
"He’s been gigantic for us since he signed for lots of different reasons, as I’ve continually said – his character, his determination to win, his experience and his versatility as well, so it’s not just one position we’re losing, we’re losing his ability to play centre-back as well.
"But it’s something we have to roll with."
Howe also confirmed Matt Targett, a possible replacement for Burn a left-back, is facing a potential three-month lay-off with a hamstring injury.
Newcastle face Dortmund on Tuesday, a fortnight after losing 1-0 to the same opponents at St James' Park.
The two sides are locked on four points in Champions League F, with Paris Saint-Germain leading the way on six points, and AC Milan propping things up on two points after three rounds of games.
Watch Atletico Madrid v Celtic in the Champions League on Tuesday from 7.30pm live on RTÉ2 and RTÉ Player, follow a live blog on RTÉ.ie/Sport and the RTÉ News app
Watch the FAI Cup final, Bohemians v St Patrick's Athletic, on Sunday from 2pm on RTÉ2 and RTÉ Player. Follow a live blog on RTÉ.ie/Sport and the RTÉ News app and listen to live radio commentary on Sunday Sport on RTÉ Radio 1.
