Leonard was making his third start for Sheffield United.
Sheffield United host Leeds United on Saturday lunchtime.
Scottish Premiership champions Celtic have missed out to Brighton Hove Albion and Preston North End already this transfer window.
HITC Sport understands Sheffield United are set to finally sign long-term target.
Sheffield United signing Middlesbrough's Adam Clayton on loan could be ideal and could allow them to snap up Southend's Ryan Leonard for free.
Will John Lundstram impressing for Sheffield United see their interest in Southend's Ryan Leonard lessen?
The Southend United midfielder is a long-term target for Sheffield United.
Southend are determined not to lose Ryan Leonard but Sheffield United are refusing to take no for an answer.
Southend have rejected another bid from Sheffield United for Ryan Leonard so should they instead look at Brentford's Ryan Woods?
Sheffield United boss Chris Wilder admits he needs cover in central midfield - and The Blades may look at Ryan Leonard again.