Complex sentence: The 1981 NBA Finals set the standard for futility, with an average rating of 6.7, the lowest in NBA history until the 2003 NBA Finals averaged a 6.5 on ABC.
Split into simpler sentences: The 1981 NBA Finals set the standard for futility, with a 6.7 average rating. The mark was the lowest in NBA history, until the 2003 NBA Finals averaged a 6.5 on ABC.