The 22-year-old was expected to play a big part in Doncaster Rovers’ promotion push.
But the Northern Ireland international now faces a long and arduous rehabilitation process after suffering a horror injury in his first pre-season run-out of the summer.
“I just have to stay positive and am waiting on a date for the operation but it could be as soon as this weekend,” McCullough told the Portadown Times.
“After the surgery we can plan the rehabilitation programme but I have support from everyone at Rovers and know the medical team is basically available 24/7 to help my recovery.
“They say it can take as long as nine months but obviously everything depends on the rehab.
“It is important to concentrate on doing everything the right way, stay patient and positive.
“To have that happen in my first pre-season game and with everyone looking forward to the start of the season is obviously awful timing but I just have to focus on the future now.
“Injuries are part of the game and, hopefully, this is my one bad setback.
“However, they say the rehab means you come back stronger than before. In the past it may have ended careers but now medical advancements mean most players make a full recovery.”
McCullough signed a new three-year contract at Rovers the day before he sustained the injury in the friendly win at York City.
“That deal at least allows me to put my full focus into the road back without fears over my future,” he said.
“It means a lot to see and read the support from the fans since the news came out.
“The manager has also just told me not to worry and to focus on getting back in the right way.
“Hopefully the Rovers lads can do the business without me and get us back up out of League Two.”