Baez can play all the positions Alcantara can play. He can actually play them better and has a stronger more accurate arm. His K% is right around 28% and thats with 2 games of 3 strikeout performances. Around 21% the other 10. His walk rate is over 9%. Alcantara is strikeout at the same rate and has a lower walk rate. Baez is beating out Alcantara.
Also, this is Baez homerun. Giancarlo Stanton is the only other player I have seen hit a ball harder. This is why the Cubs are not quick to move him. This is why people will always salivate over him. Not many players that can do that dont make it.
http://bornonthird.mlblogs.com/2015/05/12/javier-baez-destroys-a-baseball-video/
Eh... about the don't make it thing.... I'm not entirely sure I read that right but there's PLENTY of people who hit the ball hard who don't make it or at least guys with ridiculous power who aren't stars. Jack Cust comes to mind. Russell Brayan is another. I agree they shouldn't move Baez for whatever they can get. Not sure if you've seen the mets thread or not but it feels weird I'm the one of all people defending his value there.
As for positional thing, what I mean is Alcantara is probably a more versatile bench player. That's not just a positional thing. Alcantara is objectively faster. Not saying Baez is slow but if you're going to pinch run Alcantara is the guy. Alcantara also switch hits. Whether or not he actually "hits" there is another issue but having the match up edge is another area of benefit. As for the positional thing, I'd agree Baez probably can play all the positions Alcantara can but he hasn't really done it and at the very least would be rusty there comparable to Alcantara.
Regardless, I don't really see the logic behind calling Baez up to be a bench/platoon player. It's also hard for me to envision them calling him up to play LF/3B every day unless they literally start giving him looks there now. If they did that for a month in the minors then sure I suppose I could buy him coming up if he was hitting well but that doesn't really seem likely. As much as I love Alcantara's skill set and think he can be a big time player, if Cogs continues playing meh I could definitely see the benefit of Alcantara as a platoon option if he figures out his hitting issues in the next month because they have lately been running a short bench. Plus like I said, you've already burn the option year on Alcantara this year anyways. So, there's no cost to calling him where as with Baez there would be one.
That's why I view it as Baez having to force their hand Bryant style as the way he gets back barring injury or Russell just sucking for whatever reason. For example, let's say Herrera gets hurt. Why would you call Baez up to sit the bench and burn an option year? You almost certainly would call up Alcantara because you've already burned it for him and while Baez is hitting better, Alcantara probably offers you more off the bench where as Baez is probably the better every day player at this point in their respective careers.