I think that may have been the play where it looks like Kamara was on the backer on that side, started on a route, saw the blitzer and tried to re-direct to get him but by then Hurst and the pass rusher he was blocking was already in the way. Maybe it was a different play. But essentially, OL don't really 'decide' who to block so much as the follow the assignments based on the scheme and the relevant protection/slide calls. If that defender was for the RB to block, then Peat shouldn't block him because he rushes. Possibly, He would have been sliding to the A gap with the expectation, pre-snap, that the overload was on the right side and McCoy and Ruiz would have their own guys to block.
Hard to know for sure without watching the play.