Complex sentence: He began his career as an apprentice at Arsenal, turning professional in 1979; however, he failed to play a single game for the Gunners and moved north to join Barnsley in 1981.
Split into simpler sentences: He began his career as an apprentice at Arsenal, turning professional in 1979. However he failed to play a single game for the Gunners and moved north to join Barnsley in 1981.