It is almost always stupid to play two quarterbacks in a game by design. However, if there ever was an exception to that rule, this might be it. Simply put, Nania cannot be the starter because he is injury-prone and, with significant play, will get knocked out of action sooner rather than later. Unfortunate, but that is how it is. However, he could be a valuable weapon if he is injected into a game to change the tempo or to capitalize on an opponent's vulnerability against the run.
My concern is a repetition of last year. Nania returns, plays the entire game for several weeks, then gets knocked out for the season right in the middle of conference play. We then throw Wells, or Davis, or whoever into the lineup after they have been sitting for a month. No chance then.