Why do you think Percy still returns punt & kickoffs, while Tavon only does punts? What type of plays did Tavon usually touch the ball? I read somewhere 70% of his plays (and it could be much higher) were within 5 yards of the line of scrimmage. Percy is a more physical runner, with the ball. Watch him, probably explains his injury history. Tavon rarely if ever breaks a tackle....In fact, I'd bet his yards after contact is around 0.....These players while similar, are very different. Tavon was given ample opportunity to prove he was a game changing player last year...the first 6 games if I'm correct. He led the team in drops.
I don't like going on & on about Rams players in a negative light, but it would seem that 6 touches a game is probably more than enough,and until he gains more size, he should not be featured in any role besides decoy....