Pospisil was probably not going to win his single, then Canada had to make Raonic play the double to have a hope.
He was good in this double, it was a very good doubles match, and a tight one.
Canada's double surely could have won this, then Raonic could beat Tsonga.
They lost the double, Canada now had very little chance, and Raonic was painful : even if it was not that bad (which has still to be confirmed), the decision to withdraw is understandable.
Are you serious?? Raonic was anything but good in the double missing easy volleys (might as well staying back) and easy returns (same for Nestor though).
Heck, even his 1st serve % was low, clearly don't know how to play double.