Bartra. Who is a natural defender. Song played there a couple of times the last time like ... I don't know. 2 years ago? So the experience excuse shouldn't count. He isn't an experienced centre back. He is a positionally suspect CM.
Regarding Song being a suspect CM (which he certainly was at Arsenal from the games I watched) but its really mind boggling how you're reaching such staggering conclusions after just 1 game. By your logic, after his debut for us you would have had to say the opposite, since he was excellent in that match. So let's just wait a little bit more before brushing him aside as a suspect everything.
While Song wasn't the main culprit for the goals, he has to take blame for both. For the first one he should do a lot better than to get nutmegged like that by a simple cross.
Well that happened when he was playing at Center Back, so lets give him a break for now. I mean that was just a freak nutmeg, nothing else. Probably won't hapen 99 out of 100 times.
I blame him more than Alves. Alves didn't expect the ball to go through Song's legs like that. He got surprised in a split-second. Blame goes to Mascherano as well. Emaneke left him behind far too easily.
Preposterous. You blame him more than Alves when actually the exact same thing that happened to Song happened to Alves, simply caught on the wrong foot.
For the second goal he's caught in no man's land. Look at his position when the counterattack starts.
Again, put this one down to him not being a CB. The position in the pic above is where he almost always is on the pitch, force of habit. I tend to get angry when Mash finds himself in those positions.
You don't have to commit an obvious blunder like Mascherano in the Supercopa to be at fault for a goal. Bad positioning / closing down like that also counts as "shit defending". Song actually gets beaten twice in that scene as well. First he's far too high up the pitch and let's the striker run in-behind him. Second he trails back but loses the 1 on 1 again, letting the number 9 cut in with ease and play the pass which left to the goal. Adriano looked like the dick at the end but the whole move started with Song's failures. Not that I blame him. He's no centreback.
...Lets us all just relax for now and judge him after seeing him a couple more times, hopefully not at CB