If the injury was on my sub, I wouldn't use a Red pack. But my TOP Eleven has to be in perfect condition
Besides, I remember 1 or 2 cases when I let my main players rest throughout his injury, and when he came back for matches, he lost his MOJO and was only rated 4-5 at games compared to 7-8 before the injury. That said, I won't skimp on the red packs, definitely not on my scouts/ world classs players.