Giving away Erden to make roster space for Murphy was a bigger mistake than trading Perk/Nate for Krstic/Green. Of course, the outcoming of the Perk trade has hurt the team more, but at the time nobody would know if Perk was going to come back healthy, or Green's heart condition.
Erden>>>>Stiemsma
Semih was playing with an injured shoulder, and he still managed to be the second best Center for the Celtics last season, after Shaq.
I'd rather start Semih than Stiemsma, letting JO come from the bench. In fact, I'll send Stiemsma + our future (top-55 protected)2nd round picks from the Kings

Would Cleveland send us Semih back? Well, according to the article and what Sherrod said during the timeout, Semih is in Scott's doghouse.
And maybe Stiemsma is a better fit in Cleveland, after all