Despite the impossibility of starting a rookie at MLB, I believe the Bears drafted Urlacher as a safety, changed his position to MLB and started him in the cover- 2 in his rookie year.
Pure blasphemy
You obtain your studs in the draft.
If Willis is a stud in the making, they draft him with the intent to start him. If he can't hack MLB as a rookie (which I doubt), they start him at Spikes spot.