It was easy to miss. The Yankees were spending Monday — all of Monday — beating the Orioles, which is rote this season.

So within winning both ends of a doubleheader, the in-game losses were hard to detect. But in the opener, Luis Cessa began to surrender a big lead, forcing manager Aaron Boone to turn to Zack Britton and Aroldis Chapman to close it out — as he had to do with Adam Ottavino when Nestor Cortes Jr. wobbled late in the nightcap.

Twenty-four hours later, Boone was praising the importance of Adonis Rosa holding Baltimore to one run over the final two innings. Since the final was 8-3, it played like a manager going out of his way to note the work of a long-time minor leaguer in his major league debut.

That is not how it was perceived internally. The Yankees understand how fragile their 2019 pitching puzzle is. And the puzzle is complicated by this: The Yankees are the only team in the majors not to use a reliever three straight days. The other 29 teams have done it. The Yankees have not.

“We don’t have a standard rule,” general manager Brian Cashman said about deploying a reliever on a third straight day. “There’s a recognition in the importance of trying to win games, but not at all expense. If we can navigate that over the course of 162 [games], which is very difficult to pull off, you would be better for it.”

If a Yankees fan has ever been flummoxed by Boone’s bullpen patterns, it is tied to this philosophy. The Yankees would rather sacrifice the singular game than push relievers to what the organization sees as a danger zone.

For example, the Yanks had 14 pitchers on the roster Tuesday, but that was because so many were unavailable due to back-to-backs or pitch workloads. Britton was one of the few relievers available, but if he were needed to close then — because he had also worked in Monday’s doubleheader — he would not have been available Wednesday. Which is why Boone saw Rosa’s work as valuable to give Britton the day off. And, indeed, in a tighter game Wednesday, Britton successfully protected a 6-5 edge in the eighth inning.

“If you get those guys hurt you are not losing a day, you are losing a quarter of the year, half of a year,” pitching coach Larry Rothschild said. “So that one day it can look bad. But when looking at the big picture, you are going to win more games because of it.”

The Yankees have been beset by injuries this year, including Dellin Betances (shoulder) before the season began. But their four main relievers — Britton, Chapman, Ottavino and Tommy Kahnle — have stayed healthy despite logging at least 50 appearances each. Only Oakland, with five relievers, had more do that.

And how important has it been to keep the relievers sound? When all four pitched in a game, the Yankees are 22-0. When three pitched, they were 14-4. That is a combined 36-4.

“It definitely gives a better chance to stay healthy and fresh, and we still have a decent amount of appearances,” Britton said. “We are getting our work in and not being taxed with that third day. … It is definitely not a coincidence [that for the most part the relievers have stayed healthy].”

Britton noted that knowing after two straight days of work that an automatic off-day is coming allows relievers to use the day judiciously to avoid even playing catch, to get aggressive with recovery in hot and cold tubs, steam rooms and saunas, or to use it to strength train.

“Injury prevention is the holy grail of the game,” Cashman said. “You would like to think that we are putting them in a better position to stay healthy, but I can’t represent that is why they have been healthy.”

Ottavino said, “I’ve done both now and I do feel like I am fresher now than in the past. … Being proactive about it is smart. If you throw three in a row a bunch, you need days off anyway, so avoiding that is good. The policy is good and works well, and it works because of our team.”

Even without Betances, the Yankees have four high-grade relievers to share the burden, so that helps. Yet there are challenges.

The Yanks were averaging fewer than five innings a start. Some of that is about employing an opener 14 times. But it also reflects that the main rotation pieces have hardly been workhorses — the Yanks were in the bottom third of the league in starts of at least six innings with 50. Plus those 14 opener games necessitate greater relief usage.

The Yanks have played six doubleheaders, including two during a 19-games-in-17-days stretch that concludes Sunday. That is why so many extra arms have been run in, and why Mike Ford ended up pitching two innings to keep a standard reliever from logging innings and a day of work during a blowout loss to the Indians.

Plus, winning actually is a factor. The Yanks have done it so often that they have consistently had leads to protect or close deficits to preserve.

“The more you win, the more the temptation is because the wins are right there for you [to use your best guys redundantly],” Rothschild said. “If you define what it is before the game, then it is not even a possibility. … If you put those guys into those situations [three days in a row] they are not going to perform to their peak, so why use them anyway? They are not the guy you are putting out on the third day that they were the first two.”

There is an important amendment: If the Yanks found themselves in a struggle for a playoff spot in September, they would likely abandon the philosophy, and they clearly will do so in October if they get to a series in which Games 3, 4 and 5 are played on consecutive days. Britton said he mentioned to Boone that he could go three straight days — that he did so as the Orioles’ closer. But that Boone’s response was, “We’re not there yet.”

The Yanks are hoping when they are there, Betances will have joined the main four relievers to provide greater depth and protection, and that the season-long philosophy will prove valuable with still strong relievers.

“We are comfortable that the way we are [using relievers] is the right thing to do,” Rothschild said.