Why is Gio not RB1?

[grampahol]

(10-01-2018, 01:46 PM)bengalfan74 Wrote: Gio is a great, outstanding, spell back 10-12 touches a game but that's it, Long Term

And he can fill in a game here and there we're lucky to have him.

But Mixon is better all the way around

Someone really needs to explain this term, spell back.  I'd be happy to teach anyone how to spell back.. Bee, Aye, See, Kay.. 
Alright, that's out of the way.. I just don't quite get the usage in context.. Somehow I get the gut feeling it's just a made up phrase to appear like whoever is using it seem like they're saying something profound.. 
Nothing personal bengalfan74.. You're not the first person I've ever picked on for no good reason.. lol