Johnson, 20, has attracted interest from Spanish giants Real Madrid and Atletico Madrid plus Liverpool and wants to stay in top flight football.
Downing, meanwhile will have a pin inserted in his foot on Friday.
Boro's assistant manager Malcolm Crosby announced: 'Stewart is going to be out for two or three months at least.'
Red alert: Johnson's future at the Riverside is in doubt after the promising winger snubbed a new contract
Birmingham move for Balde after admitting Boro's Wheater is too pricey We won't sue you! North-East trio deny they'll take legal action against United MIDDLESBROUGH FC