Manchester United's Ole Gunnar Solskjaer is forcing himself through the pain barrier to salvage his career.
Solskjaer, 32, hopes to return to action in August - after missing the season recovering from knee surgery.
He has started jogging for the first time and knows he must push himself through the pain battier.
"I have no pain with the light jogging but I still have to force some discomfort through the knee to stimulate it," said the Norwegian.
"I could have gone 12 months without feeling anything but then when I started playing again it would have been sore. So you have to force a little bit of pain because that is the nature of this injury."
Solskjaer went to Sweden for a transplant operation that entailed extracting cells from his right knee, growing them in a laboratory for three weeks and then putting them back in the hole in his cartilage.
"The transplant is maturing and now for the next two or three months it needs stimulation forced through it gradually.
"The light jogging has been the next step, but I am not jumping or sprinting yet. The next step will be to run 100 metres. But when that happens you don't know. There is no specific timescale.
"You are governed by how it reacts each day. It is a slow process and you have to be very patient," he told the Manchester Evening News.