After having made 13 wartime appearances and scored eight goals in the 1918/19 season Matthews made his official first-team debut for Liverpool as a centre-half in a 3-0 win over Derby County on 3 April 1920. "Big, burly and boisterous" Billy played as a forward in his other eight appearances for the Reds. Matthews revealed to a reporter at the Derby Daily Telegraph: “Liverpool think I will make a centre-half, but I know I never shall. It is not in my bones to play there!" Matthews scored three goals in two games at the beginning of the 1921/22 season but in the following five matches he only got once on the scoresheet and didn't get another chance to prove himself at Liverpool who went on to win the League that season and the next. 

In March 1922 Matthews joined second division Bristol City but was relegated in the spring only to bounce back immediately as the club won Third Division North. He wanted to move closer to his childhood home despite having to stay in the third tier of League football and joined Wrexham in 1922/23. He drifted into non-league football two seasons later but only spent four months in the Cheshire County League and went back into League football with Barrow and eventually Bradford Park Avenue where he gathered his third Welsh cap. He made 112 League appearances for the Bradford club and won Third Division North in 1928. Matthews was a fitness fanatic and a keen cyclist into his nineties and was known as "Billy white hat" because of the distinctive headgear he wore.