You can't control the paint if:
1) The other team can consistently break down your defense because your bigs are both too immobile to defend the pick and roll
2) The other team scores easily in transition because your bigs are too slow to get back
Playing JO and Shaq together would also be horrible for Rondo. Think of all the points we get when KG runs hard in transition, or even Perk. Shaq and JO will be like Wallace, alway trailing well behind the push.
It is true that no one will grab rebounds over the heads of those two, unlike with Baby, but there are so many things we could substitute fr the word 'rebounds' in that quote.
1) Didn't hurt the Lakers. Bynum hurt his knee in 1st round, and still managed to make his presence felt with one knee. Size matters in the NBA. Don't underestimate our Perimeter D.
2) Transition offense is back-court job. With occasional KG outlet pass.
Team up: KG with Shaq & Baby with Jermaine.
I trust DOC.
The backcourt guards against fast breaks, but it isn't their job to avoid 4 on 2 transition defense. The big guys need to get back to even numbers.
I'm not underestimating our perimeter D. That isn't even at question in my post. What I doubt is our pick and roll when JO or Shaq show. They can't get back to their man after hedging. They are too slow.
I am fine with one of those two on the floor, but not both together. The problem with not playing both together is that Shaq is a disruptive force when things don't go his way. If not for that, I would gladly take Shaq as insurance.
There is a reason why JO has a higher market value these days than Shaq. Shaq has a bit of AI in him and has a hard time accepting a diminished role.