Hard-throwing left-hander Felipe Rivero is one of the few true bright spots in the Nationals’ bullpen as opening day approaches. (Katherine Frey/The Washington Post)

Of all the red-flag, buckle-your-seat-belt, duck-the-subject phrases in sports, maybe none serves more purpose and gives a clearer warning of turbulence ahead than these five words: “It is what it is.”

So, Nationals, what do you think of your bullpen? The chorus here, from team executives to players: “It is what it is.”

Context is everything with our new friend IIWII. Sometimes you’re so awful you refuse to make yourself more miserable by talking about your team’s problem. Hey, it is what it is.

Sometimes circumstances, such as injuries, are beyond your control, so you’ll soldier on. Please, cut us a little slack. It is what it is.

But frequently you’ve done your best, so dear lord, don’t let anything else go wrong because it’s probably too late to make it much better. It is what it is. The Nationals fall into that last category.

This is, supposedly, the era of the beastly bullpen, led by teams such as the world champion Royals, Pirates and Yankees, who have at least three relievers who could all be closers. “We feel like we have a seven-headed monster [in the pen],” Pirates left-hander Tony Watson said recently.

How many “monsters” do the Nats have? Let’s open the box marked “objectivity.”

FanGraphs and Baseball-Reference have sophisticated models to predict performance. Here is an average of their projections for the ERAs of the Nationals’ eight most likely relievers: 3.16 (Jonathan Papelbon), 3.37, 3.41, 3.46, 3.57, 3.65, 3.85 and 3.92. Competent pros: eight. Monsters: probably zero.

And those are the Nationals’ best relievers. When injuries come, they’ll use several more who’ll probably have a combined ERA over 4.00. So, on paper, you’re looking at a team ERA over 3.56 — which would have been ninth in the NL last year. In other words, maybe not quite average.

In contrast, the best seven St. Louis relievers last year pitched 264 innings with a 2.18 ERA, which carried the Cards to 2.82 ERA for all of their relievers.

In Nationals camp, all topics elicit various degrees of optimism — except the bullpen. The main reason: All seven men will be tasked to the limits of their previously documented abilities to handle the jobs to which they are now assigned. This isn’t like 2014 when Rafael Soriano, Drew Storen and Tyler Clippard could all say, “Make me the closer!” And every other role was “overqualified.”

At every ’pen slot, the Nationals have issues. None that can’t work out well. But look at the sheer number. First, at 35, Papelbon is long in the tooth for a closer. He may save 46 games at that age, as guileful Lee Smith did; or maybe he’ll save only two and disappear like fast-crashing Soriano at 35. In hulking size, adaptation of style and lost velocity from near-100 to perhaps 92, Papelbon resembles them both. “Well, I like the Lee Smith comparison,” Papelbon told me.

Second, the Nationals are counting on two kids in their second full year — lefty Felipe Rivero and Trevor Gott. “Gott is a power guy who sits at 95-96 and has touched 100,” GM Mike Rizzo said. But Gott, 23, was in a battle just to make the team against Matt Belisle, 35, a cheap-and-available $1.25 million free agent. Belisle made the team on Tuesday. So Gott, acquired for Yunel Escobar (.314 in 2015), may start in Class AAA.

Rivero may need to be a back-end standout quickly, especially if others fail. Does Rivero, 24, have the thick hide and bullet-proof-vest temperament to take over a major role?

“He’s left-handed, throws 97-98. Good slider and change. Throws strikes. Not scared. How much time did K-Rod [Francisco Rodriguez] need?” Rizzo said. “That kind of stuff improves your ‘temperament.’ ”

Next issue, three or four spots will go to pitchers who define “journeyman.” The past three seasons combined, Shawn Kelley, Oliver Perez, Yusmeiro Petit and Belisle have ERAs of 3.80, 3.54, 3.66 and 4.20. Popular ex-Nat Sean Burnett, trying for a comeback, is in the same career category. Perez, 34, finished last year badly with the Astros. Petit, Perez and Belisle came at modest cost. But after the Nats lost to the Orioles for free agent Darren O’Day, they gave a three-year, $15 million deal to Kelley — set-up man money. Good luck to him, but I’m mystified. He’s 31, has had two Tommy John elbow surgeries and throws 55 percent sliders, a tough pitch on elbows.

Finally, there is the touted but so far merely useful Blake Treinen, 27, who has a 0.00 ERA in spring training and may benefit from new pitching coach Mike Maddux. Actually, who might not profit from Maddux? In Treinen, Rivero and perhaps Gott he has “big arms” to work with. He’s done lots with less.

My provisional nickname for this pen is The Disposables. Except for Rivero, the kind of lefty who’s a long-term investment, there’s no need to baby ’em or be too patient if a trade upgrade appears.

“There’s often a big turnover in bullpens. Relievers tend to travel,” Nationals Manager Dusty Baker said. “There are lots of [great] relievers who moved a lot. Lee Smith was on [eight] teams.”

Mariano Rivera pitched only for the Yankees. But the other 22 relievers with 310 saves played for an average of 5.2 teams each. Hall of Famer Goose Gossage had saves with nine teams. “They have an off year, they get traded. Or they have a great year and are about to get into the money, so they let you leave,” said Baker. “It’s a tough life. Don’t unpack your bags if you’re a reliever.”

Assistant GM Bob Boone, who won eight gold gloves as a catcher, says, “I think Papelbon will be like Soriano in ’13 [when he saved 43 games at age 33 for the Nats]. He’ll get the job done, but it might not be as pretty as it used to be.”

What about the rest of the ’pen? “We’ve got some live young arms and some good veteran experience,” Boone said. “It is what it is.”

But, as the Nats and their fans will start finding out next week, what the heck is that?