I mostly agree with Goony. But it's really on the Cubs. If they use the available data they have and determine it's not a safe bet that he's going to produce, they have to find someone else. In the very extremely limited time he was up, he didn't look good although the underlying data looked okish.
However, they also should not throw out another tomato-can retread at 1B next year in the hope that he will produce at some rate better than the unknown.
I think Mervis deserves a legitimate chance if the Cubs can't find a legitimate MLB player in the offseason (I'm dreaming of Pete Alonso like Tom dreams about Ohtani).