Complex sentence: Simpson had the best game of his career during the Thanksgiving game against the Detroit Lions on November 25,1976, when he rushed for a then record 273 yards on 29 attempts and scored two touchdowns.
Split into simpler sentences: Simpson had the best game of his career during that season's Thanksgiving game against the Detroit Lions on November 25. In that game, Simpson rushed for a then record 273 yards on 29 attempts and scored two touchdowns.