you can run deep out of the slot too its all how your offense is designed. I don't get why people say because he is fast he should only play on the outside well what kind of fast is he. TJ graham would probably not be good in the slot because he is not very quick he has good straight line speed, but Goodwin can run all the routes and when matched up with the slower slot corners and possibly linebackers it is a mismatch. in a cover two defense the two outside routes will have a safety on top and you can use a fast receiver like Goodwin to split the safeties. there are infinite possibilities of coverages and formations to say that a player cant play in this position or that position.