The 20-year-old’s loan switch to Bramall Lane has been agreed in principle, but Chris Wilder’s side wanted Riley to prove his fitness following a hamstring complaint before the switch is sanctioned.
As The Star revealed, Riley emerged as target for Wilder and his staff after Jose Mourinho granted him permission to leave Old Trafford on loan.
The midfielder, who can also operate at full-back, is understood to be keen to join United on loan and Wilder’s decision to not offer Reece Brown a new deal earlier this month suggested he was confident of tying up a deal for Riley soon.
Riley has made two senior appearances for Mourinho’s men, after progressing through the ranks at Old Trafford. Louis van Gaal, Mourinho’s successor, handed him a first-team debut in the FA Cup against Shrewsbury last year.
Meanwhile, the Old Trafford giants have been linked with a move for Blades youngster David Parkhouse.
The highly-rated 17-year-old, a Northern Ireland youth international, signed for United in 2014 and said at the time: “I couldn’t have asked any more of Sheffield United.
“My education, my accommodation and everything is being sorted out to our satisfaction.
“I’ve got my foot in the door and the hard work starts now.”
Nick Cox, the former head of United’s Steelphalt Academy, now works at their counterparts in Manchester and, according to ESPN, has vouched for Parkhouse’s abilities.
Luke Fedorenko is also moving to Old Trafford, and Bramall Lane officials are advertising for the academy head of recruitment role he leaves behind.
Full details are on United’s website, at www.sufc.co.uk.