Complex sentence: He became a first team regular, and was called up into the Dutch under-21 team, however a longterm injury forced him to miss out the whole 2001/02 season and most of the 2002/03 season.
Split into simpler sentences: He became a first team regular, and was called up into the Dutch under-21 team. However, a long term injury forced him to miss the whole 2001/02 season and most of the 2002/03 season.