Complex sentence: He was called up to the Under − 21 squad for the first time in March 2015, making his debut in the 54th minute of a 3--1 win over Bulgaria in Cardiff.
Split into simpler sentences: He was called up to the Under − 21 squad for the first time in March 2015. He made his debut in the 54th minute of a 3--1 win over Bulgaria in Cardiff.