Fess, on the radio, just said he went runnin to be pulled from the last play: "They are gunna foul, and I not too sure I can make 2 free throws, like Frank."
That sounds like a frank acknowledgment of his own limitations. I'd prefer that to the guy who insists on playing and then loses the game.
To be honest, Fes had played a lot of consecutive minutes to that point anyway. I wouldn't be shocked if he was a little gassed. Sloan, however, read the situation correctly and saw that Fes was making a big difference in the Jazz getting stops.