Well I think the specialty of the PR manager is very low, and I hear that the extra points your team can gain from having a specialty is just like...2-3 points. So unless it's a really really close game, the effect is minor I think.
But ofc it is still an important external support for your team. For example my first league match where I won by 1 point. Without my Crowd Involvement PR manager, I may have lost the game.