Sunderland manager David Moyes has admitted it was a massive blow to lose midfielder Jan Kirchhoff to injury during Saturday's 1-1 draw with West Brom.
The former Mainz man sustained the injury after landing awkwardly when contesting an aerial ball.
The midfielder was celebrating his 26th birthday on Saturday, but his party was over early as he had to be helped from the field of play, appearing to be in a lot of pain.
"Not to have him, Steven Pienaar and Adnan Januzaj is massive, because they help us play better and we are short in that area. They are big, big misses to this club," said Moyes.
"If we lose Kirch and we lose Catts, we lose a little bit of the steel and a little bit of the boys who have been here before while we're looking to build a new team."
Kirchhoff has only just returned from a spell on the sidelines after a hamstring injury kept the big German out of Sunderland's opening four games of the season.
Sunderland rescued a vital point from the game, but the Black Cats find themselves in the relegation zone, having gathered just two points from seven games.
"I'm really disappointed not to get all three points, but it wasn't for the want of trying, and it wasn't for the want of the players doing the best they can, and maybe the players are doing the best they can," Moyes added.
"If they're doing their best, then that's all you can ask for.
"They kept going and tried to find a way through and deservedly got one back."