Being 33, this inevitably casts doubt over his footballing future.
Brown joined Sunderland in July 2011 on a four-year contract for a fee of £1m.
Martin O’Neill: “It has been really tough for Wes, a real challenge.
“He’ll do a few days training, he does a few days here and there, and then he has a setback and it has been really frustrating for him.
“But all he can do is keep on trying.
“It’s not what he would have expected when he first got injured and I feel for him.
“It’s a shame for the lad and it’s hard for him to take.”