"I have stuff going on with my back and trying to figure out the best way to go about it is," Holmes said.
"Felt like it was the smartest thing, to give it a break and try to play it smart and not try to push through something where it could be a lot worse than where it's at," Holmes said.
The 29-year-old said he has not undergone any tests and that he would be able to come back quickly if he did end up on the injured list.
"It's definitely frustrating to deal with at this moment," Holmes said. "Just for the fact that's kind of where we're at, but I think this is probably the smartest move. I think there's definitely going to be another guy that can step up and I believe whoever it is we have full trust. I think we play our best baseball when we need to."
Holmes was one of the best relievers in baseball through the first half of the season, putting up a 1.37 ERA and a 2.00 FIP through 39 games and 39⅓ innings pitched, earning an appearance in the All-Star Game after taking over as the team's closer when Aroldis Chapman went on the injured list and breaking Mariano Rivera's franchise record for consecutive scoreless appearances.
Things have gone south as of late for Holmes. Since July 12, Holmes has appeared in 11 games, posting a 10.24 ERA, allowing 11 runs in 9⅔ innings pitched while striking out 11 batters and allowing 10 walks.
The struggles for Holmes have pushed Boone into a "mix and match" strategy for the closer spot, relying on Scott Effross and Chapman for late-inning relief. Other options could include Lou Trivino, Wandy Peralta, Jonathan Loaisiga and Albert Abreu.
The Yankees' bullpen has faced injury issues to some of its top performers, including Chad Green, who underwent Tommy John surgery; Michael King, who underwent season-ending surgery to repair an elbow fracture; and Miguel Castro, who was placed on the injured list on July 14 because of a right shoulder strain.