Gaizka Mendieta is continuing to train with Middlesbrough - though he has not been allocated a squad number.
"But while he's here we'll treat him the right way, he's an excellent professional.
"He's got a little bit of an injury at the moment so he's not training with the rest of the team but when he's fit he does."
Former £30m man Mendieta, 33, who is in the last year of his Boro contract, has previously been linked with moves to the USA and a return to his homeland.
"Hopefully from his career point of view he can get something resolved," added Southgate.