Strachan just about wrote off his hopes of keeping Johnson at the club saying "it is out of my hands ... if he goes he goes".
And the former Celtic boss has told his players they can no longer live in Johnson's shadow and must raise their game to his level.
The new manager has recognised the hugely important contribution made by Johnson so far this season and wants the winger’s team-mates to also stand up and be counted.
Strachan: “I think he’s more than a key player now.
“If you look at the stats you realise how important he’s been to the club. We need to keep him playing as he is, but the rest as a group have to say: ‘you have a day off and we’ll take over’.
“We must as a group be a more rounded team.
“If you look at our performances he’s huge at the moment."
Sunderland seem to have the edge on the likes of Everton and Bolton, should a deal come about in January.
Steve Bruce says he will be first in with an offer, and Johnson wants to stay in the north-east.