Folk, once again, you miss the part of how the defense and the offense, work together in the big man/swingman combo.
In the big man scenario, his defenses are supposed to be focused on patrolling the paint and controlling the boards. KG, albeit, a great rebounder, plays like a supersized guard or point forward, than a big man, because his defenses are either circa the high post or nearing the perimeter than where he needs to be, the low post. Then, you might say ... ok, we have Perks. Well that great, now let's have someone monkey w/ KP's shoulder (or have him run around for a while, thus beating on his ankle or simply wear out his cardiovascular conditioning) and then, the opponent has a new strategy ... clog the paint and the Cs defense (followed by offense) will come to a halt. Yes, Ilgauskas, Wallace, Gasol, & the coaches are aware of this technique.
Thus, when push comes to shove, the Celtics now have three guards: Ray, Garnett, & Rondo. The 1st is either hot/cold (& typically needs to come off a screen), the 2nd (pass first but a mid-range jump shooter), and the latter, a guy who can mainly do a layup. Do you see the problem with the above, we have a donut team, when under pressure, but we're suppose to have a top tier PF/big man on our squad?
But instead of seeing the above, which is kinda apparent, fans always fall back to ... 'but he's 20+ ppg / 10+ rpg' and 'Wally sucked during the Wolves time'
In a true big man->to->swingman combo, clogging the paint, simply doesn't suffice, as a choke off strategy. Instead, it'll be a combination of the opponent getting hot, followed a defense which minimizes the touches that either the big man or the swingman, can receive during a certain possessions. Or if its a suffocation defense, then 2 of the other Celts players will be more or less, wide open. If those 2 players can't hit a wide open shot, well, it's game over.