It’s been expected for some time that Anthony Rizzo’s DL stint would last the minimum 10 days, and that appears to be the case. While the Cubs can’t yet make the corresponding move official, the MLB transactions page shows that they have optioned Efren Navarro to AAA Iowa.
Navarro was called up when Rizzo went on the shelf with a stiff back, so this is a pretty clear indicator that the opposite is taking place now. Unless, that is, the Cubs have been so pleased with the work Kris Bryant is doing at first that they are happy to swap Navarro for someone else.