Yankees manager Aaron Boone said Marinaccio would not be an option for the upcoming American League Division Series but could potentially return should New York advance to the ALCS.
"We decided we're going to put him on the IL, hoping that he would be eligible if we get to the championship series," Boone said before Tuesday's doubleheader against the Texas Rangers.
Marinaccio was escorted off the field during Sunday's 3-1 loss to the Baltimore Orioles and had an MRI that showed the stress reaction. He also had an MRI on the injury earlier this season, but testing came back negative.
"The shin thing's kind of just been a lingering issue I've been dealing with all year," Marinaccio said Sunday before the MRI.
The rookie reliever was hopeful that it was just a product of late-season "wear and tear," but Boone explained that the club opted to go the conservative route.
"[Marinaccio] definitely wants to try and pitch through it. And there's probably even some thought that he could pitch through," Boone said. "It's kind of a gray area, but you also worry about it turning into a stress fracture or does it compensate him in other ways as well. So we've made that decision to go ahead and IL him."
Marinaccio has been an integral part of the Yankees' bullpen this season, allowing 10 earned runs over 44 innings for a 2.05 ERA with 56 strikeouts.
"He's had an outstanding season, been an important part of what's gone on down there," Boone said. "And again, hopefully we get him back if we can advance to the next round and this time can be valuable and get him just a little bit healthier and stronger and we'll continue to evaluate that."
The Yankees already are missing key bullpen pieces, with left-hander Wandy Peralta (back) and closer Clay Holmes (shoulder) not available until the start of the ALDS on Oct. 11. Both currently are working out at the Yankees' alternate site in Somerset, New Jersey,.
Boone said Peralta was scheduled to throw live batting practice and that Holmes would start his throwing program Tuesday for the first since receiving a cortisone injection for inflammation in his right rotator cuff.
"Obviously, losing Ronnie, at least in the short term, is a blow," Boone said. "Optimistic that we're getting Clay back, getting Wandy back -- feel really good about how some guys are throwing back there. We feel like we have a lot of really, really good options. It's probably not going to be those traditional roles as we roll to October, so we'll just mix and match what we feel like is a lot of great options."