Klay having a bad game doesn't really surprise me. He has been playing for the same team since he got drafted, so it will take a while for him to get adjusted to his new team, dude changed teams at 30+ , of course he doesn't know how to play with them. Plus they are missing a crucial player as well.
I believe Klay will get better over time, while I agree this was a terrible game from him, it doesn't mean he is going to stay like this. Realistically speaking, he never had any good season starts neither, and after a few months we are going to see him be a great part of this team without a doubt. With everyone healthy, and playing together, this will not be a big deal and we are going to see them do fine eventually. This doesn't feel like something we can make a big deal out of yet, just because of one bad pre season game.