The Sheffield United striker has only featured 19 times this season - his last outing was on January 14 - due to injury.
United have now sent the 32-year-old to the FA’s Burton centre to try and help his recuperation, after opting not to have surgery on his ankle.
Boss Chris Wilder is confident the former Sheffield Wednesday striker will recover to help the Blades before the end of the season.
“There’s only Leon out, and he has gone to St George’s this week, for a week, to step up his rehab,” said Wilder, ahead of Saturday’s League One trip to Rochdale.
“Sometimes, a different venue just gives them a little bit of a boost. He’s there this week and will come back to us next week.
“They didn’t know whether they were going to operate, or inject it, and they have injected it. There’s progress, which is good for him.
“I feel he will be back before the end of the season, 12 games to go, eight weeks of football.
“He and us have both got a desire to get him back playing as soon as possible.”
Joe Riley - on loan from Manchester United - has had an operation on his dislocated shoulder, confirming he will miss the remainder of the campaign.
Wilder said: “Joe’s had an operation, so he’s out for the season. That’s no surprise.
“That was a sensible decision, for everyone, and for Joe’s long-term future.”