Devastated at being left out of the Brazil squad for the Tournoi de France, the midfielder fears he could miss out on his country's defence of the World Cup next year.
"I would like to resolve this problem as quickly as possible. I have to think of my career," he said. "I must be part of the World Cup squad, but I did not get picked for the Tournoi, which upset me. I know I have to go away and play well. It would be easier for me to get back if I play in Spain. At home more Spanish football is watched than Brazilian football."
That would appear to make Atletico Madrid the favourites to sign him, but Middlesbrough's chief executive, Keith Lamb, has denied that the Spanish club had made the pounds 12.5m offer that was reported.
In any event, Juninho made it clear he was not certain to leave England. "I enjoy playing in the Premiership," he said. "It is not true I rejected Manchester United, they are a big club who are in the Champions' League next season.
"I have to see Middlesbrough first whatever I decide, but afterwards maybe I can think about it."Reuse content