O'Neil out for season
The Scottish international, who has featured prominently for North End this season, has suffered a knee injury which requires an operation.
"Brian O'Neil has a problem with his left knee. We have been to see a specialist in Crewe and that has shown he has a small defect on one of the bones," Preston physio Andrew Balderston told the club's official website.
"That is bad news because, one he is going to require an operation and secondly, he is going to be ruled out for four months so he won't be back until pre-season and will be a massive blow between now and the end of the season."
O'Neil suffered problems with left knee earlier in his career, but Balderston insisted this was a new injury.
"This is a brand new problem," he continued.
"He has been having intermittent pain in his knee for the last five to six games but it has only really been the last two weeks when it has affected him to any real degree.
"After the game on Saturday he couldn't fully straighten his knee. The scan was already booked for Monday because we knew that we had a problem with it.
"It is the knee that he has previously had two operations on before, two cartilage and one cruciate ligament reconstruction but apart from this small area, the bottom of the femur looks very, very good considering all the operations he's had and the amount of time and games in his career he's missed because of this."
Manager Craig Brown was understandably downbeat when he heard the news.
"I'm very disappointed to lose him because he has been and is an influential figure in our team but the consolation is that this will cure the problem, which has given him the problem, on and off, for the last couple of months," he said.
Meanwhile, Preston have suffered further bad news on the injury front - as Marlon Broomes is sidelined for four weeks with knee ligament damage.