I think it's as simple as Joerger is trying to improve our defense. The death knell for Bjelica was when we traded for Barnes. Out goes Bjelica at PF and in goes Barnes, at least to start the games. I think Joerger got tired of seeing the opposition waltzing down the lane for easy baskets when Willie had to switch in the pick and roll, and no one (Bjelica) came over to guard the lane. At least three times last night, when Willie switched, and did a show on Westbrook, Barnes rotated over and stopped the pick and roll.
Of course when Paul George got two easy baskets shooting over Bog's, they brought in Bagley at the PF position, and then Barnes switched to George. George ended the day with 14 pt's on 19 shots, and 5 of those points were on Bag's. Our overall defense has improved with Bjelica on the bench and Barnes on the floor. That's not to say that there won't be times when Bjelica will be on the floor. But too many nights he was a liability on defense, and would end up the night with 5 or 6 pt's. You can live with poor defense from a player that's putting up 15 to 20 pts a night, but not 5 or 6 pt's