Trea Turner, center, is one of many young Nationals who are poised for stardom in a few seasons — or sooner. (Jonathan Newton/The Washington Post)

When the Washington Nationals go to the World Series in 2018, this will be their lineup: Trea Turner (shortstop, .300, 50 steals), Michael A. Taylor (center field, 20 homers, 30 steals, Gold Glove), Bryce Harper, Ryan Zimmerman, Anthony Rendon, Daniel Murphy, five-tool Victor Robles (left field, the No. 63 prospect in MLB at 18) and Pedro Severino (a defense-first catcher).

Their rotation: Max Scherzer; Gio Gonzalez; Tanner Roark; 6-foot-6, 255-pound Lucas Giolito, the top pitching prospect in baseball; and Joe Ross, a stellar rookie in 2015. The bullpen will have four men who have notched triple-digit fastballs — lefty Felipe Rivero, Blake Treinen, Reynaldo Lopez and Trevor Gott. Erick Fedde, the Nats’ No. 1 pick in the 2014 draft, fits in that frame somewhere, too.

Or, at least, that’s how the Nationals see their future. Every team has a grand design. But as Mike Tyson said, “They all have a plan until you hit ’em in the mouth.”

The Nationals are great at 1) depth chart projections on grease boards like the one above and 2) getting hit in the mouth when it counts most.

But that doesn’t change the facts: All those players are aboard. By 2018, it would be a very good, very deep, very cheap roster, so free agents could replace whatever parts of the puzzle don’t work out.

This season? Come on, you know you want candor. The Nats are probably in transition. They had a four-season window (2012-15). They won a ton of games, third most in MLB, and built a following. There were cheers and tears, magazine covers and World Series predictions that didn’t come true.

Then last offseason, they blew up almost half of the team, if you include the manager, key coaches and the medical staff. They’re still recognizable and probably 88 wins good, give or take. But you usually don’t go to the Series with a loose cannon like Jonathan Papelbon as your closer and six guys named “U, V, W, X, Y, Z” behind him in the bullpen. Lightning could strike. But it doesn’t happen often.

The relevant question about the Nationals right now is probably not whether they will win the National League East, though they might. More likely it is: How do the key kids look? How fast will they arrive? When will they become front-line contributors? What’s their ceiling: good or exceptional?

First, Giolito. Pundits with no skin in the game clamor for a quick arrival. Don’t count on it. Oh, those darn Nats, acting sensible again with a young flamethrower. At 21, with a year of development lost because of elbow surgery, he needs Class AAA innings — a summer to master fastball command and hone a change-up. But if a starter is lost for the year, if Giolito’s ERA at Syracuse is 2.00, well, you never ever know.

Patience is probably going to be required with Turner, too, though he’s MLB’s No. 11 prospect. “Trea — the world is his. It’s just a matter of when,” Manager Dusty Baker said. “Would you like to have him here now? Oh, hell, yeah. But would you be stunting his growth and hurting his progress?”

Oh, heck, probably. But it pains Baker to talk down Turner even a tad. “That little boy can hit that inside fastball as hard as anybody on this team,” Baker said. “And he ain’t that little. People talk about little, skinny Trea, but he weighs about 185 pounds, right? Same size I was when I came up. And I could knock the dog crud out of that ball.”

Turner’s maturity on the subject only muddles the picture because it makes you suspect that he’s actually psychologically ready. “I don’t want anything handed to me,” Turner told me. “Don’t step on toes. Don’t make a fool of myself. Stay under the radar. . . . If it happens, it happens.”

Other questions will get answers quickly. The most pleasant surprises here have been Treinen (0.00 ERA in nine innings) and Taylor (16 for 33 through Tuesday). “Oh, I’m hoping it’s real,” Baker said of Taylor’s softball stats.

Because the Nats need both bullpen heroes and a sixth starter in case of injuries, Treinen has the potential for double impact.

“Treinen has great demeanor. He’s a jewel of a person,” Baker said. “I just urged him to have a little more dog in him this year.”

As in junkyard dog, one who knocks those left-handed hitters off the plate so he can open up the outside corner. “You know what ‘dog’ means,” Baker said when pressed. “That’s a compliment, man. Guys go, ‘Hey, wassup, dog?’ You don’t say, ‘Wassup, cat?’ ” Nice deflection.

“The organization is in love with his stuff. The world was, actually,” Baker added, since every trade inquiry seemed to include Treinen. Then why does he give up so many hits?

“There’s a bunch of guys like that — until they figure out how to use all four quadrants of the zone, the [right] sequence of pitches,” Baker said. “Curt Schilling, Nolan Ryan, Randy Johnson — outstanding stuff, but until it all came together, hitters think, ‘I don’t know how I’m hitting him, but I’m hitting him.’ ”

It must be March: Treinen just became Ryan.

Should Taylor, forced by injuries to be the regular 2015 center fielder, be a fourth outfielder who must force his way into more playing time? Is Ben Revere good enough to hold him back?

“Taylor wasn’t overmatched last year, even though we had to rush him to the majors,” General Manager Mike Rizzo said. “All year, nobody came up with bigger hits at bigger times than him. He’s a plus-plus center fielder who’ll steal bases and has power and a strong arm.”

But when, if ever, will he bring his scary ratio of 108 hits to 158 strikeouts into roughly 50-50 balance? Of the 11 Nats with the most at bats in 2015, seven had more hits than whiffs. It’s not easy. But it’s not that hard either. If Taylor gets there, “then he’ll probably be a superstar,” Zimmerman said.

Taylor spent part of the offseason studying film of himself. Why had he been so good in the clutch? “I relaxed more in those situations,” he said. Does he know how rare that is?

“I watched every double and homer — my body language was different, more positive,” Taylor said. So now he’s focusing on not squandering at bats in sleepy low-leverage situations. Also, all day “I try to feel confident — believe I can play well even when I’m not. Don’t let the negative thoughts creep in.”

When Baker looks at his entire group of 21- to 25-year-olds, he says, “They’re [all] ahead of their graduating class — that [age group] that would have gone to college or played minor league ball together.

“They’re way ahead of schedule. Now we have to increase their learning curve.”

Should Dusty get kudos if they improve?

“I don’t need credit. Ain’t looking for none,” he said. “Just victories and a handsome paycheck.”