Sunderland defender Dion Sanderson will miss the rest of the season because of a back problem.
The 21-year-old, who is on loan from Premier League side Wolverhampton Wanderers, has been ruled out for six weeks with the injury.
He made 27 appearances and helped the club to the verge of a League One play-off spot with three games remaining.
"It's a big blow, but I don't think about those types of things in that way," boss Lee Johnson said.
"I look at it as a challenge, otherwise it's 'woe is me' - and it's not about me, it's about the team and giving someone an opportunity or adjusting it.