I think the reason for the use of Clark more is that Tony noticed a team like the Rams had a great passing offense but the following years the teams in their division started to load up on CB's to combat their great passing attack. Now the Rams aren't what they used to be. Tony and his staff realized this and which their offense to use the TE more because a TE can man handle a CB, whereas Stokley can't. They just switched their offense around to keep the defenses guessing. I'm sure Stokley doesn't care as long as they get to the super bowl that's all that matters.