Trey Sermon's success at Ohio State isn't guaranteed.
That isn't a reflection of his talent (which is readily apparent), or his importance to the Ohio State offense (which will be paramount), or Ryan Day's desire and ability to integrate him into his system (which will be extremely high). Instead, it's an acknowledgement that all of those things aren't necessarily a given, despite what we've seen from the Buckeyes and Sermon in recent years.
Trey Sermon is absolutely a talented running back. There's no real doubt about that; he has all the physical tools to succeed and recently passed the first significant milestone on his way towards becoming a full-fledged star in the Ohio State offense.