I was watching Tim Duncan yesterday
Lately i've been observing the late game plays of certain teams, so yesterday I was watching the Lakers/Spurs game because I was particularly interested in what they would do down the stretch against Kobe and the Lakers.
My first thoughts in the last couple of minutes were "what the hell is Roger Mason jr. doing on Kobe? are they retarded?" and sure enough, Kobe starts going off. Now, if you just watched the game highlights you probably saw Mason's game winning shot + foul shot, but what you may not have seen was Duncan aka Mr. Reliable down the stretch.
They passed it into Timmy twice with the game on the line, and he has such a wide array of moves that it's nearly impossible to stop. He can make a strong move with his back to the basket, pump fakes, hook shots, go glass, and even take the mid-range jumper with the game on the line. In this case he made a back to the basket hook shot to bring them within one I believe. Then they gave it to him again and he made another one to put them ahead one, before Kobe made the 3 and Mason had the go ahead 3 point play.
But my point being, Bosh is not a go-to player, very similar to what KG was before coming to Boston. When Bosh gets the ball down the stretch everyone and their mother know exactly what he's gonna do. Either: catch the ball, pivot and do a step back fadeaway jumper, or pump fake a bunch of times and try to take his man off the dribble. A guy who stands back a little, stays on the ground and keeps a hand in his face essentially takes away both of these moves with relative ease.
So, my point in all of this is that for all of the talk about guard play, the typical thing to do with the game on the line is to give the ball to the teams best player (whoever that player may be) and let him go to work. Bosh just doesn't have the game to do that, and not necessarily just because he's a power forward.