It's only 10% of the season but Baez is ranked 11th in MLB in Fangraphs' advanced SS stats (tied with Andrelton Simmons). He has more range and a much better arm than Russell (who ranked 13th last year), and he's only going to get better at SS if he's left along there long-term rather than moved around. He's clearly in a very good place as a player right now - it makes no sense to change his situation dramatically by turning him into a utility player again.
As you can see in the link below from 2015 thru 2018, Andrelton Simmons is far and away the premier defensive SS in MLB. So, obviously, looking at 1/10 of this season so far and ranking him #11 (with Baez) and trying to make a point about Baez with that stat is not a great use of statistics.
As you can also see from the link, since Russell came up in 2015, Russell is #2 in MLB behind Simmons at SS in Defensive Runs Saves (DRS). Even though he has significantly fewer innungs than superb defenders Lindor and Crawford (among others), Russell still has more DRS than they do. Aside from Simmons, there is a very strong case to be made that Russell is the premier defensive SS in baseball.
Russell is a better defensive SS than Baez, hands down.
On the other hand, I totally get the argument that Baez’ overall game is blossoming to such an extent that you just leave him alone and don’t change anything with him now, at SS. Have always believed that, with your premier, elite players, you put them where they give you the best value and where they thrive—-and work the lesser guys around that.
Russell is a better SS than Baez but obviously a lesser overall player now.
So, will be interesting to see how Cubs play this out. Don’t see Cubs moving Russell to 2B but maybe he becomes the utility guy with Baez getting more SS starts than Russell. Not crazy about moving Baez around at this point....but perhaps he is such an outlier guy that moving around has zero effect on him and he’s just as good no matter what you do with him.
https://www.fangraphs.com/leaders.aspx?pos=ss&stats=fld&lg=all&qual=3000&type=1&season=2018&month=0&season1=2015&ind=0&team=0&rost=0&age=0&filter=&players=0&sort=13,d