Complex sentence: There were no MLB All-Star games prior to 1933, as the All-Star game is not played exactly at mid-season but about 90 games in (the full season is 162 games).
Split into simpler sentences: There were no MLB All-Star games prior to 1933. Also, the All-Star game is not played exactly at mid-season, but about 90 games in (the full season is 162 games).