It's not an opinion that a quarterback needs to be able to grip and hold the ball with both hands to play quarterback. That's a fact. The Saints being in the playoffs doesn't change that fact.
That's an actual opinion and it's obviously your opinion.
It wasn't pain that kept him from being able to grip the ball with his left hand, it was an issue of strength. The damage in his hand weakened his grip. Shooting up wouldn't have made his grip better. Now, maybe rubbing some dirt on it would have helped.