Montero (0-1) allowed four runs (three earned) in the 10th inning and picked up the loss to San Diego on Wednesday. He allowed one hit and two walks before ceding a walkoff grand slam to Manny Machado.
Montero entered the game in the ninth inning when the score was tied, so it was not a save situation in the 10th after Texas took the lead. The Rangers' closer had not allowed an earned over his first five appearances but couldn't keep the Padres off the board. San Diego worked the first two walks of the season off Montero.