Protection is key. Protectors will typically be build better to avoid hits and for taking a hit and have high resilience. Without protection your normal players who are prone for higher damage on hits will be easier targets.
Try to place your protective players close by your strongest and/or most prone players with low resilience. Also take into account which areas of the field your opponent is trying to target with his brutal players.
On the tactics page a full blue line means your protector will step in nearly always when the player the line is drawn towards is targeted by your opponent for a brutal hit. Dotted lines means that the protector only steps in "sometimes".
Watch out for playing too many protectors if you are behind. Protectors focus on defense where you will get a bit stronger for each protector you have on the field, but it will also hurt your possession.
Playing more protective players when you are winning in a match can therefore be a smart strategy often. Having a protector or two on the bench is a smart idea if you wanna park the bus late in the game.
If your protectors are better than the opponents brutal players you will also quite often get extra attacks as the protector blocks the way for the assisting player to move forward and create a chance.
If you have a superstar who is not protective himself, always keep him well protected. He will most likely be the player your opponent will target with his brutal players to hurt you.
If your opponent does not have any brutal players on the pitch, you have no need for protective players unless you just want to boost your defense and don't mind giving up possession.