[4] After playing local football, Matthews was taken on trial at Swansea City but suffered a broken arm and was told to come back when he had recovered from the injury.

[9][10] His performances earned him a regular starting spot in the side, missing two matches in the following two months, including scoring his first senior goal during a 4–0 win over Watford on 3 October 2009 when goalkeeper Scott Loach misjudged Matthews' 50-yard free-kick, allowing the ball to bounce into the net.

"[13] On 25 February 2011, Celtic announced they had secured the signing of Matthews on a pre-contract agreement to commence on 1 July, on a four-year contract.

[19] After an impressive start to the season, it was reported that Premier League clubs Fulham and Everton were interested in signing Matthews in the January transfer window.

New Sunderland manager, David Moyes, deemed Matthews surplus to requirements at the Stadium of Light and he rejoined Bristol City on a season-long loan on 28 July 2016.

[29] Matthews signed a one-year deal with Charlton Athletic having been training with the club for a number of weeks after leaving Sunderland at the end of his contract.

[34] He joined League of Ireland Premier Division club Shamrock Rovers on 28 January 2025, signing on a free transfer.

"[35] Matthews made his début for the Wales under-17 side on 28 February 2008 in a 1–0 win over Austria and played in two out of the team's three matches during the 2008 UEFA Under-17 Championship elite round.

[38][39] His next participation at youth level for Wales came when he was called up to the under-21 side for matches against Hungary and Italy, but remained on the bench in both games.

On 9 November 2009, Matthews was called up to the Wales senior squad for the first time in his career for a friendly against Scotland at the age of seventeen,[40] but remained on the bench.

Four days later, Matthews made his début for the under-21 side when he played 45 minutes in a 2–1 defeat to Bosnia and Herzegovina before being substituted due to a foot injury.