Maples was optioned to Triple-A Iowa on Thursday, Mark Gonzales of the Chicago Tribune reports.
Maples was in competition for a spot in the big-league club's bullpen, though he'll now presumably start the season in the minors. He threw sparingly prior to the suspension of the Cactus league, striking out three and walking one across two innings of work. Maples has pitched for the Cubs in each of the past three seasons, so he'll likely serve as bullpen depth at some point once the campaign begins.