I think Sully is playing hurt
I think this could be the case as well, possibly, but even healthy he has some flaws. If so, the decline started after 3/20/16. Right now his assets do not outweigh his liabilities. Were this to be case, I think people would be more lenient.
or he has gained too much weight
If this is case, it is completely inexcusable. The man is a professional athlete. I have zero sympathy if this is the case. Enough, is enough. Stress fracture last year, 4 years of being overweight and out of shape. Time for him to make like a baby and head out! COMPLETELY UNPROFESSIONAL. What happens to you and I if we can do our job? We get fired.
He can barely get off the ground. The fact that he can't get an offensive rebound against a terrible rebounding team has to be evidence that he isn't 100%.
Horford has won many matchups against him, but his poor has been through the month of April to present. He never was a leaper but it is worse than usual.