Its right you don't really go all out in the nets, but how else could he prove fitness before hand, they couldn't replicate the situation. I would have imagined that the medical would have gone through all the processes and scans before hand, but there was still a weakness there.
Being a bowler down and with the release of pressure and the added tiredness of the remaining bowlers has in this moment let Australia get to a higher score than they should have done. In a venue that England generally win at, they are at a sure disadvantage now.