Complex sentence: Matches of this type are often used to help managers select players for the competitive matches of a tournament and, if the players usually play in different teams in other leagues, it's an opportunity for the players to learn to work with each other.
Split into simpler sentences: Matches of this type are often used to help coaches and managers select players for the competitive matches of a league season or tournament. If the players usually play in different teams in other leagues, exhibition games offer an opportunity for the players to learn to work with each other.