I don't want to suggest that the trade didn't have real negative effects on the team.
But...before Perk stepped a foot on the court this year, Boston was 33 and 10. That projects out to a record of about 64-18 for the season. They finished the season 56-26. Perk played 12 games with the team and they went 8-4. In other words, this team started to suffer on the court AFTER Perk came back.
Now, the trade certainly wasn't the only thing that happened to hurt the Celtics, but Doc's words show that one of the biggest problems was that this stubborn, stuck-in-their-ways team let the trade affect them mentally and emotionally.
Mike