Montgomery was optioned to Triple-A Scranton/Wilkes-Barre on Saturday, Erik Boland of Newsday reports.
The move appears to be on a temporary basis, as reliever Ben Heller was recalled to provide some bullpen depth prior to the upcoming All-Star break. Montgomery allowed two earned runs over a rain-shortened 4.1 innings Friday and the Yankees won't need a fifth starter until July 17, so he'll be removed from the active roster for now. The young southpaw finishes a productive first half of the 2017 campaign with a 3.65 ERA and a 1.23 WHIP to go along with an 87:28 K:BB.