I don't know if this theory rides completely. It doesn't really work in a "we can't outplay them, so let's out-muscle them" way - because the same methods are used by many small clubs against bigger opposition. Arsenal aren't particularly unique in that respect. But they could be getting more physical attention because they are perceived to be one of the weaker - physically - sides in the league. That could make it a target, set out by opposition management, to physically rattle Arsenal players, and it could mean they get crunching tackles worse than Utd or Chelsea, leading to more serious injuries, like this one, and similar leg breaks received by Diaby and Eduardo in the past four years. However, it's a bit of a stretch and I think it's as much a case of coincidence and ill fate as a neat passage of causation.