What a difference a win streak makes (not to mention a 56 point win over a team in turmoil). To put this in perspective, let’s take a look at where they were.
On Thanksgiving-eve, the Celtics were 13th in the league in net rating (1.5) mostly bolstered by a defensive rating of 102.8 (2nd in the league). The offensive rating was 104.3 which ranked them 27th in the league.
They have clearly turned things around offensively. This is partly attributed to an easy schedule, but these are the same kinds of teams (and the Knicks were the same team) that tripped up the Celtics earlier in the year.