Dusty doesn't have a choice. Montero is on the team and is filling a role that needs to contribute innings. The mistake was overpaying Montero.
Situationally pitching him against the heart of the Mets order was a very poor decision and it played out like he we all thought it would. How many games does Montero have to blow for Dusty to learn? Stubborn as a mule.
So....you wanted Montero to come in with 2 men on and a 2-run lead or be saved to close out the game?