Adam signed for Sunderland from Scottish champions Celtic in July 2015 after spending four years north of the border.
The Welsh international won a host of honours during his time in Scotland, lifting the SPL trophy in four successive seasons and twice being named in the PFA Scottish Team of the Year.
A pacey full-back who loves to get forward, Matthews initially caught the eye for schoolboy side Cardiff City, making his league debut at 17 and quickly establishing himself as a first-team fixture.
His strong performances for the Bluebirds earned him the Championship Apprentice of the Season award in 2010, alerting a host of clubs in the process. Celtic won the race to his signature in 2011 and Matthews instantly established himself as an important part of the side as they won the SPL in his first season.
Matthews drew attention in 2012 when his outstanding display helped the Bhoys to a famous 2-1 victory over Barcelona at Celtic Park. After being capped for Wales at every youth level from U17 he made his full international debut in 2011, appearing as a substitute in a Nations Cup tie against Scotland.
Matthews has subsequently gone on to make 11 further appearances for his country.
A clean striker of the ball, Matthews has developed an ability to score stunning goals, with his first senior strike for Cardiff coming via a 50-yard free kick and his first for Celtic also coming in similarly spectacular fashion.
The defender made two early-season appearances for Sunderland in his debut season and later joined Bristol City on loan, making nine appearances for the Robins.
Adam then spent the 2016-17 campaign on loan at Ashton Gate, returning to the Stadium of Light and regularly featuring during the following campaign.