Sunderland midfielder David Vaughan has revealed how doctors were left baffled when trying to diagnose the injury that hampered his pre-season with the club.
Vaughan, 29, missed the first month of the Black Cats' Premier League campaign after undergoing surgery for what was originally believed to be a hernia problem.
"It was a hernia-type of thing, but it was more of a tight nerve in my lower stomach," Vaughan explained.
"It was a rare injury really and the physios, doctors and even the surgeon had never seen it before so it was a bit unusual."
"No one knows how it came about, but I was carrying it for the last few months of last season. I should have tried to get it sorted, but because of the rarity of it, no one knew what to do with it."
The Wales international admits he was aware of the problem towards the end of last season, but decided to play through the pain in order to help the Black Cats - something he now concedes may have done him further damage.
"At times, I was aware of it when I was playing, but it's difficult to pull yourself out when you feel you can still do a job," He said.
"Maybe, I shouldn't have played as much towards the end of last season, but that's with the benefit of hindsight."
"We were hopeful that with a bit of rest, it would have sorted out. But it didn't make any difference really so I needed an operation after pre-season started."
Vaughan returned to the Sunderland bench for the visit of Aston Villa last weekend, with the former Blackpool player convinced the club can turn their recent poor form around.
"On the training ground, the players don't seem to be doing anything different," said Vaughan.
"Confidence is quite high and it's just a case of turning training into performances at the weekend. It's down to the whole team to give our attacking players the opportunities to shine.
"We've got players who on their day could win any game for us. Maybe they're struggling a bit at the moment, but I'm sure it will turn around.
"With the squad we've got, we should maybe be doing a bit better. But there's still a long way to go this season and when we hit a bit of form, we should see the side start to do well."