I liked Gabriel, but if he's as good as people here seem to think he is then he'll be at a bigger club in no time.
The bloke didn't learn a word of english while he was here and is as thick as shit. Physically he had everything you'd want in a CB (being a few inches taller wouldn't have hurt) but the guy made mistake after mistake. He had plenty of chances and fucked them all.
Being better than that clown Mustafi isn't a reason to pine over someone. We may as well bring Djourou back if that's all it takes, he loves the club so much he'd probably play for free.