Complex sentence: While his minutes per game went down in Chicago (28.1 during the 1980-81 season; he had never averaged fewer than 34.6 previously), he averaged 14.1 points per game; however, this would be his last effective season.
Split into simpler sentences: While his minutes per game went down in Chicago (28.1 during the 1980-81 season; he had never averaged fewer than 34.6 previously), his production during those minutes did not. He averaged 14.1 points per game; however, this would be his last effective season.