They exited Madison Square Garden with a clear answer about where they stand: far behind the Celtics, who routed the Knicks 131-104 just like they did in October. The 27-point setback — New York’s largest of the season — was eye-opening. The Knicks had won seven of eight before Saturday’s game and were 1½ games behind the second-place Celtics in the Eastern Conference. “Unacceptable,” said Knicks captain Jalen Brunson, who scored a team-high 36 points on just 18 shots. “We’re not where we want to be.”