Middlesbrough had been toying with the idea of keeping Johnson – out of contract this summer – for the remainder of the season.
The Teessiders know that holding onto the talented 22-year-old gives them their best chance of promotion.
And the vi
ew at the Riverside was that if Boro could gain promotion back to the Premier League, they could then make Johnson an offer he'd find difficult to refuse.
If Johnson leaves in the summer, Middlesbrough are entitled to a compensation fee because he is under 23.
But the Easington-born winger turns 23 in July and there is the prospect that he could move abroad, in which case Boro would be entitled to absolutely nothing.
The Teessiders know it will be virtually impossible to hang on to the winger and the belief is hardening that the club have to cash in on him as much as possible by letting him go in January.
Should he leave, there will be no shortage of top-flight takers,but Sunderland are in a very strong position to sign a player who is settled in the region and who feels a pull through family towards the Stadium of Light.
