Middlesbrough goalkeeper Mark Schwarzer says the boo-boys could drive Stewart Downing out of the club.
"Stewart's a great player and if he looks elsewhere because of what's been happening then he'd be a big loss for the club."
During crisis talks with boss Gareth Southgate last week, Downing admitted the jeers were getting to him.
"Stewart should only leave this club for football reasons - not because he has people on his back," said the Aussie keeper.
"Players thrive on confidence and what you hear from the crowd can erode that at times."