I think this is exactly the point that I was trying to make earlier. By taking Manuel over Nassib, regardless of what Marrone thinks Nassib's potential is, be it HOFer, franchise QB, reliable starter, stop-gap, backup, or training camp fodder, he thinks the difference between the two is significant enough to warrant choosing the unfamiliar over the known commodity. If the difference was minimal, Nassib's famiiarity with Marrone and his offense alone would be enough to warrant taking him over Manuel. Whatever difference the FO perceives between Manuel and Nassib, it's not subtle.