The Cubs optioned Barnes to Triple-A Iowa on Monday.
Barnes was called up for the second time of the season Sunday, but he did not pitch in the Cubs' 6-0 loss to the Dodgers. The Cubs reinstated Phil Maton (knee) from the 15-day injured list Monday, and the big club will send Barnes back to Triple-A, where he has appeared in five games (two starts) with a 3-0 record and a 3.24 ERA, 1.36 WHIP and 19:8 K:BB across 16.2 innings.