He is a 2nd rd back up WR. If he can't play on STs cut him. My heavens Dion Jordan the #3 overall pick plays on STs.Me either.
We're 5 deep at receiver, and chances are the returner will have to come from them. He also has really great vision on returns. It's also really stupid to prevent a rookie who has not proven his worth on offense (yet) and who is not a starter at his position from contributing on ST.