"The last four or five months have been a hard time. But ever since I've been at the club the fans have shown nothing but support for me.
"That's why I'm desperate to repay them. I owe them a hell of a lot.
"Not just the fans but the manager, the staff and the players. No matter what we achieve over the next three-and-a-half years of my contract I will never be able to repay the debt of the backing they've given me through good and bad times.
"If we win every trophy in that time it wouldn't be enough to repay them."
Keane said United, who went trophyless last season, couldn't suffer the same fate this campaign.
"We can accept one year without a trophy but two is unthinkable.
“Sometimes I run around like a headless chicken. That might be a bit harsh, but it's not far off. I've not played well enough for the last year-and-a-half now, despite what anyone else says.
"It's true that the injuries I have suffered haven't helped - that's not an excuse; it's a fact. But I'll be using my head a bit more from now on. I don't want to come back with the daftness I had before. I don't mean the bookings - they happen. Sometimes as a player I need to look at the bigger picture rather than wanting to do everything by myself. I want to be crossing, defending, clearing off the line - and it's just not possible."