Skysports.com reports that Sunderland are trying to sign Middlesbrough captain George Boateng.
Sunderland are understood to be among the clubs keen on capturing Boateng, who was left out of the New Year's Day defeat to Everton.
Boro boss Gareth Southgate suggested he would be reluctant to lose the former Aston Villa midfielder.
"He is our player and we have got a small squad," said Southgate. "We are not in a rush to lose any of our players.
"It's a bit of a strange one at the moment, but we have just got to deal with it."