In spite of being just 19, Johnson has managed to impress with his performances at senior level, having already accumulated six Scottish Premiership appearances for Motherwell.
It was the youngster’s goal that proved to be the determining factor in Motherwell’s 2-1 win against St Mirren on Wednesday.
However, Johnston has fewer than four months remaining on his current contract with Motherwell and is being tracked by at least three clubs south of the border.
Apart from Sheffield United two other clubs, Preston North End and Luton Town, want to sign Johnston, though the Scottish club are not keen on letting him go.
Motherwell will look to whoever they appoint as their new manager to try to convince Johnson to stay put.
That could be tough given the lucrative terms likely to be on offer in England.
And Sheffield United could well be a Premier League club by the end of the current campaign.
