Sunderland signed defender Adam Matthews from Scottish Premiership champions Celtic for £2million.
The 23-year-old full-back has signed a four-year deal with the Premier League club, who announced the move on Friday.
"We know that we need quality players to improve competition for places in the side, so Adam is a welcome addition to our squad and we are very pleased to welcome him to Sunderland," he said.
Sunderland sporting director Lee Congerton added: "Adam is a player we have been tracking for some time.
"Even though he is only 23 years old, he has a wealth of experience, and I am sure he will continue to improve under the leadership of Dick Advocaat."
LATEST ARTICLES
