Yeah absent info we don't have like an injury(however legitimate in the case of Alzolay), I think it's Brewer. He's had a couple decent outings most recently but on the whole hasn't been anything special, he doesn't offer platoon advantage and is clearly at the bottom of Counsell's pecking order.
Plus the likelihood of him being needed again is not terribly high and neither is the downside of exposing him to waivers. If we got to his spot in the Iowa shuttle again, you have no shortage of other options that could be considered next time. From journeyman starter types(Teheran, Straily) to waiver wire fodder(McWilliams, Carl) to legitimate prospects of varying roles(Horton, Hodge, Cuas), there's likely to be someone favored above him at that point.