United had looked set to bring the 25 year-old to Bramall Lane in time to stake a claim for a place in Wilder's team for the challenge of the Championship, but an agreement couldn't be reached with his club.
However, it was the performances this season in the wake of the proposed move breaking down that maintained Wilder's belief that Leonard would fit into his squad and personal terms have now been agreed with the player.
Leonard will undertake a second medical today, the first part having taken place before United's FA Cup success against Ipswich Town on Saturday, and should be available to go straight into the squad to face Sheffield Wednesday on Friday night.
Outlining the qualities which persuaded him to bring Leonard to United, Wilder highlighted the way the player coped with seeing the move fall through in August, saying: “It went public, which we can’t do anything about. Clubs do that to try and get an auction going for the best price which is fair enough. But he wanted to come here straight away.
“We’ve watched him all season and he’s been their best player. That tells you what he’s about. He’s not smashed the door down, he’s been a true professional and done his job. He’ll do the same for us.”
Meanwhile, Charlton Athletic manager Karl Robinson has confirmed he was preparing to try and sign United’s Samir Carruthers on loan before Roland Duchatelet, the Londoners’ owner, refused to sanction any new arrivals after putting the club up for sale.