Complex sentence: During the regular season they were 40--1 (.976) in front of their home crowd, their only regular-season home loss occurred on December 6,1985, to the Portland Trail Blazers, by the score of 121--103.
Split into simpler sentences: During the regular season, they were 40--1 (.976) in front of their home crowd. The Celtics' only regular-season home loss occurred on December 6,1985, to the Portland Trail Blazers, by the score of 121--103.