Diplan was designated for assignment by the Brewers on Monday, Adam McCalvy of MLB.com reports.
The move clears a spot on the 40-man roster for Jordan Lyles, acquired in a trade from the Pirates in a corresponding move. Diplan is considered at least a fringe prospect, with a good fastball and changeup but shaky command, but he hasn't fared well in parts of two seasons with Double-A Biloxi, recording a 4.79 ERA and a 14.2 percent walk rate in 114.2 innings.