Complex sentence: He made his competitive debut on 9 August, scoring a hat-trick in a 4--1 victory over Port Vale in the EFL Cup; in doing so, he became their player to achieve the feat in his first game since Carl Shutt in 1989.
Split into simpler sentences: He made his competitive debut on 9 August, scoring a hat-trick in a 4--1 victory over Port Vale in the EFL Cup. In doing so, he became the first Leeds player to score a hat-trick on his debut since Carl Shutt in 1989.