Johnson has been used in different roles at the Riverside, and Southgate admits he could try and work the 20-year-old into his team to head off interest from the likes of Liverpool, Tottenham and Everton.
"Adam is a fantastic talent and I do not want to see him leave," said the Boro boss. "Maybe I may have to find him a new position. I'll have to look at that. I know he can play on the right. If we alter how we play in the middle of the park that might help Adam and Stewart play together in the same team.
"I am not afraid to let people go on the basis that they might come back to haunt you. It might mean certain players have left here, had to go to get first-team football, which they would not have achieved here. But Adam could be very, very special and I would not want to see him play for another club."
Southgate admits sometimes it is not effective to blood youngsters too early, something Boro have done with great success in recent years.
"The hardest thing for some of our younger players is that they have got in the team too young in terms of having had more Premier League exposure than really they are ready for," said Southgate. "Adam is a classic example of that. He got in the first team at 17 or 18 and I do not think he was ready to go in there. It means that three years down the line he is only 20.
"He has been around the first team for three years and he does not feel he is progressing, but he has had more involvement in the first team than most players of his age. Lee Cattermole is the same."