Man Utd must sign Jadon Sancho, the world's best young player - Rio Ferdinand

At 20, Sancho is already an England international and has established himself in the Borussia Dortmund first team following a move from Manchester City when he was 17.

United have been in negotiations with Dortmund over the proposed transfer of the player but talks have stalled over the structure and cost of a deal worth around £100 million.

Dortmund's sporting director Michael Zorc earlier this week claimed that Sancho would be staying at the German club next season, but similar statements were made before the sale of Pierre-Emerick Aubameyang to Arsenal and other players.

Speaking to BBC Radio 5, Ferdinand called Sancho, the "best" young player in the world.

"He is fantastic. If he does come he'll be an added value in terms of quality no doubt," he said.

"Manchester United need top players who are going to have an effect on their first XI and I think Jadon Sancho falls into that category.

"If you look at successful Manchester United sides over the years, successful periods, there were players fighting for every position and if you substitute one out and you brought one in there was no change in the quality or the output."

Ahead of United's Europa League semi-final against Sevilla on Sunday, Ferdinand praised the reversal of fortunes under Ole Gunnar Solskjaer, saying their positive attacking play has been a revelation.

"That's been the most pleasing point," he said.

"He's ticked a box in terms of getting the team back into the Champions League, which I think would have been his remit at the beginning when he got his hands on the reins."