U.S. pitcher Tanner Roark throws during a first-round game of the World Baseball Classic against the Dominican Republic. (Lynne Sladky/Associated Press)

Last week in the Washington Nationals’ spring training camp, there was chatter about March Madness and who had picked which college basketball team’s name out of the hat that Ryan Zimmerman passed about in the club’s spread pool. The World Baseball Classic was mentioned, but usually as an afterthought.

That has been turned on its head now that the United States team has reached the final four — equaling the furthest the U.S. team has gone in four WBCs. But of vast interest to the Nats is the identity of the starting pitcher in Tuesday night’s semifinal game against Japan: their own Tanner Roark.

“The guy deserves it,” reliever Blake Treinen said. “He’s a proven, complete pitcher with elite talent, but the media and most fans probably don’t know it. I think Tanner enjoys being under the radar. It’s just extra motivation for him.

“I’ll be tuned in,” Treinen said, grinning, of the 9 p.m. game from Los Angeles.

Said Bryce Harper, who has two U.S. gold medals at the junior level: “I just found out he was starting. That’s awesome! Very cool. It’s an incredible honor to play in a huge game for your country and against a great team like Japan.”

Few big league pitchers deserve a moment in the international spotlight more than Roark, drafted 753rd in 2008 and obscure until he got a chance to start in 2014 and went 15-10. Even that showing didn’t keep him in the Nats’ deep rotation, and he struggled out of the bullpen in 2015. But last year, his 16-10 mark fully validated his ability.

In fact, since he arrived in 2013, Roark has the eighth-best ERA (3.01) in baseball among all pitchers with 500 innings, ranking just behind Max Scherzer (2.95) and Jon Lester (3.00) and just ahead of Chris Sale (3.04), for whom the Nats tried to trade half the franchise last winter. Because he induces such weak contact and avoids solid contact (two different skills, believe it or not), gets lots of double-play grounders and avoids home runs, Roark’s style deflects attention.

But not among the Nats, who hope their buddy is about to have a coming-out party. However, they also have their fingers crossed. Roark has gotten to pitch just 1⅓ innings for the United States in two weeks with the team. How sharp can he be with all five of his pitches, especially when that variety of “plus pitches,” as well as command of them all, is his basic advantage? How much stamina can he have built up? On such a mega-adrenaline stage, is his arm’s health in jeopardy?

“It’s about time!” fellow Nationals pitcher Gio Gonzalez said of the long-awaited start. Actually, Tampa Bay’s Chris Archer, who was with Team USA in the first round, then left to go back to spring training, “made himself available” to grab the Tuesday night start, but Manager Jim Leyland politely let Archer stay where he was.

“He was put in a tough situation,” Gonzalez said, “but I think they’re going to see the real Tanner Roark. He’s the most underrated right-handed pitcher in baseball. I know he’s ready to go. That guy is trying to grab the ball right now. Knowing him, he probably wants to go all nine innings.”

Roark’s bulldog personality may be the only thing about him that concerns his teammates.

“Tanner attacks, not scared, a fierce competitor,” the Nats’ Chris Heisey said. “He really likes taking the ball. Everybody says they do, but I think he really believes it. His mentality makes him a great man for the job. Hopefully his body and the sharpness of his stuff follows the mentality.”

That’s the rub. Many of the best players in the majors decline to play on the U.S. team because of exactly the kind of treatment Roark and National League MVP runner-up Daniel Murphy have gotten this year: almost total neglect of their needs for preseason preparation.

Jayson Werth, who apparently took a lifetime supply of truth serum over the winter, summed up the privately held opinion of many in the Nats organization.

“I understand this [WBC] thing is a big deal,” Werth said. “But we have two of our main guys playing in it — a starting pitcher and somebody who’s going to hit third or fourth. One of them has six at-bats in two weeks. The other has pitched one inning and now starts a game.

“I’m failing to see how this whole thing is worthwhile. I understand that it’s ‘something,’ but . . . it hasn’t done us any favors as a major league team.”

Werth’s pointed words expanded on similar sentiments from Manager Dusty Baker over the weekend regarding the Nationals players’ lack of game appearances. Baker’s overall view of the WBC is among the cheeriest among big leaguers, plenty of whom have distinctly mixed feelings about being beaten in three previous WBCs by passionate international teams, many in peak shape, while MLB players were nowhere close to regular season form and severely disadvantaged.

Nationals bench coach Chris Speier “was saying we should have had this in our day,” Baker said. “This is some exciting stuff. They are really representing. . . . That would have been cool.”

Baker quizzes reporters on whether they’ve seen the previous night’s WBC games and asks, “Well, what were you doing if you weren’t watching that?”

Baker, however, missed one of the best WBC games Saturday night, when the United States advanced to the semifinals by beating, and eliminating, the mighty defending champion Dominican Republic, 6-3, in a game that ended just before 2 a.m. on the East Coast. The U.S. was helped by a leaping catch by center fielder Adam Jones robbing Baltimore Orioles teammate Manny Machado of a homer, as well as a barely sub-orbital home run by Giancarlo Stanton.

“If I can’t stay up for the 10 o’clock news, I can’t stay up till 2 a.m.,” Baker said.

Veteran reliever Joe Nathan, eighth on the career saves list, played in the first WBC in 2006 and called it “more of that playoff atmosphere. I loved it. Tense games. Just really cool. It’s not hard on a reliever. We go on adrenaline anyway.

“Your concern is for the starting pitchers. In spring training they are on cruise control. Now it’s, ‘How am I getting these guys out?’ You need all your pitches working. You have to grind. You can start forcing stuff. That’s not good.”

It’s not essential to ask Roark how he feels. I already did last summer when we talked about the possibility that he might start a winner-take-all playoff game.

“I’ve been thinking about exactly that since I was a little kid,” he said. “I want to be that guy with the most pressure — all you can pile on. I’ve always heard, ‘He can’t do it. He’s not good enough.’ Every time I go out there it’s, ‘Prove ’em all wrong. Make ’em eat their words.’ ”

Will that include words in Japanese calligraphy?

For more by Thomas Boswell, visit washingtonpost.com/boswell.