You can definitely make the case that when he is on, this team is almost unbeatable. That is the definition of valuable.
You can also say he's not the same player without KG. Perk is definitely not. The team defense is definitely not.
You can also say Pierce is the MVP, heart and soul of this ball club. He was the best player in the world last June, and he is an offensive horse down the end of close games.
You can also say Ray is quietly having the best season of them all. How many big, big shots has this guy made for us? MVP caliber.
We can all go round and round on this. It's a great problem to have. They're all very valuable to the team.