When you go looking for reasons this team lost you can look at a bunch of things:
Timelord, Smart, Kemba and Fournier out.
The unforced turnovers being so high. I can live with forced turnovers that the opponent's great defense creates. Hats off to them. But the shear amount of unforced turnovers is unacceptable.
The refs made some crucial bad decisions that cost the Celtics dearly. The gold tend on a block by Romeo. A missed offensive goaltend by Chicago. 2 fouls that Brown didn't get that should have sent him to the line. A few other calls.
Too many times this team had Brown and/or Tatum on the court and they weren't touching the ball for many times down the court with bad offensive players trying to do more than they are capable of and the team didn't score. With 4 of the top six players out, both Brown and Tatum should have shot the ball 22-25 times.
But....that last part said, the biggest problem was simply the post NBA MVP, Jayson, couldn't hit his shots. That really is the biggest reason.
That's not to say it's all Tatum's fault the team lost. He was magnificent in everything else he did and if he wasn't playing playmaker this team loses by 15.
But 3-17 is the outlier for me.