A metric that mathematically determines how many games a basketball team should have won in a given year, based on their offensive and defensive scoring totals. One can then compare a team's Pythagorean Record to their actual record, to see if the team overachieved or underachieved that season.
Pythagorean Record is so named because of its similarity to the Pythagorean Theorem in geometry. Bill James is credited with the development of the metric Pythagorean Record, although his version was used to evaluate baseball teams. Daryl Morey was the first to use this concept to evaluate NBA basketball teams.
Using a team's Pythagorean Record, one can create an "expected" number of team victories for a season. If this number varies much from the team's actual win total, deeper research may reveal why the team did better or worse than their Pythagorean Record suggests they should have. Good luck, bad luck, or poor performance at the end of close games are just some of the reasons for a disparity between a team's Pythagorean and actual record.
Some examples of Pythagorean Record include the 1976-77 Portland Trail Blazers, who had 55 Expected Wins that season, but won only 49 regular season games before heating up in the playoffs and winning the NBA Title. The 1983-84 Boston Celtics had a Pythagorean Record of 57-25, but actually went 62-20 on route to their NBA Championship that year.