thats my personal opinion - he looked like a beast whenever i watched him and i did watch Barca regularly, as probably most polish football fans thanks to Lewandowski transfer.
Stat wise - i wont be able to prove that, Bremer defensive stats look better i must say. Might be due to different playstyles of the teams too.
Its my personal opinion, but i remember, before injury, when i considered him the best defender in the world for some time.
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also to be totally clear - he was responsible for the Barca exit from the CL last season - made stupid last man standing tackle on Barcola which led to the red card. He was bashed for this by the guys like Gundogan, but it seems he never accepted the criticism for this (even backfired at Gundo if i remember correctly). I found it totally stupid, because it was his clear mistake.