o'shea has revealed his concern at the increasing force of rugby 's collisions after harlequins and england full back mike brown was consigned to even more time on the sidelines to recover from the latest high-profile head injury .
brown has not played since the final round of the rbs 6 nations on march 21 , is still suffering headaches after a week-long holiday in dubai and no closer to being declared symptom-free .
` it 's a concern because i do n't like someone coming in with something you ca n't diagnose , `` it 's six to 12 weeks out .