Treinin was named the team’s closer shortly before the Nats headed north for Opening Day. (Photo by Katherine Frey/The Washington Post) (Katherine Frey/The Washington Post)
Sports columnist

Three springs ago, Matt Wieters arrived at Baltimore Orioles camp with a new reliever to break in. Zach Britton had come out of the bullpen just twice in 109 minor league appearances, just two more times in 48 major league outings. He was a starter by trade, and he had struggled. With the rotation full up, the Orioles needed to hold on to his talent, so they moved him to the bullpen. By that May, he was the closer.

“At first, until you get some saves under your belt, you don’t know,” said Wieters, who then served as the Orioles’ catcher and now will play the same position for the Washington Nationals. “Once you get some of those experiences built up, you have things to look back on. But at first, you don’t know.”

This is pertinent in Washington because the Nationals’ season opens Monday. When it does, Wieters will be behind the plate, and if the club carries, say, a 3-2 lead into the bottom of the ninth, the bullpen gate will swing open and out will walk Blake Treinen, a closer for the first time in his life.

A mostly uneventful spring for the Nationals concluded with the one major decision the club had to make: Who would pitch the ninth inning? The Nats chose Treinen, like Britton a former minor league starter, like Britton the owner of an atomic sinker, like Britton completely unproven at the spot.

And like Britton, Treinen will have Wieters helping navigate unfamiliar waters.

“It’s a good resource,” General Manager Mike Rizzo said.

This isn’t the reason Washington signed the veteran catcher after spring training started. But Rizzo knew that, before Wieters worked with Britton, he had teamed with Jim Johnson, another failed starter who became a successful sinker-balling closer in Baltimore. So when Rizzo went to visit Wieters at his Atlanta-area home before the catcher agreed to a deal, he asked the former Oriole: “How do sinker-ballers attack the ninth?”

“As a scout, I’m looking at his stuff, and I’m like, ‘It’s really good stuff. Throws strikes. He puts it over the plate. He’s got that heavy, heavy sinker. Should be really good,’ ” Rizzo said of Treinen. “Now, that sinker is sometimes hard to command. . . . Sometimes you have to learn how to control the sink and then learn when to throw a good sinker for a called strike and when to wipe you out with a sinker when you’re ahead in the count.”

Unlike when Britton took over as the Orioles’ closer in May 2014, Treinen has experienced success as a reliever, posting a 2.28 ERA in 73 appearances last season. But it hasn’t been a straight path. On July 19, 2015, Treinen entered a game the Nationals trailed 1-0 against the Dodgers in the ninth inning. His job: Hold the score right there. He got one out, allowing six base runners and four runs.

The Nationals sent him to the minors. As they did, Rizzo met with him.

“I said, ‘Do you know how good your stuff is?’ ” Rizzo said. “I told him, ‘These hitters are taking food off your table. You’ve got to stop that.’ That was the biggest thing with him. Ultimately, I don’t know if he knew how good he was.”

Which was, too, one of Britton’s problems in Baltimore. What Wieters helped Britton do for the Orioles — and what he hopes to help Treinen do for the Nats — is become comfortable with the pitch that defines each of them, that hard, downward biting sinker that comes in at 95 mph or faster.

“Just as far as a sinker, you don’t see many as good as Blake’s, and you don’t see many as good as Zach’s,” Wieters said. “And Zach really learned how to command it any time he wanted to and control it any time he wanted to. You can see Blake has the movement on his that he needs. It’s just going to be once he gets comfortable in the closing role, just being able to command it any time in pressure situations that he wants to.”

In his final season as a starter, Britton threw his sinking fastball two-thirds of the time, mixing in a slider and change-up. Last year, when he posted a 0.54 ERA, saved all 47 of his chances and was an all-star for the second straight season, Britton used his sinker 92.2 percent of the time — highest of his career, according to data provided by the website FanGraphs.

So Nationals Manager Dusty Baker can say of Treinen, as he did Friday, “You can’t just make it on just one pitch, but you got to have a dominant pitch.”

Treinen hasn’t yet come to rely on that dominant pitch the way Britton does — or, not to get too hyperbolic, the way former Yankee and future Hall of Famer Mariano Rivera did with his cut fastball. Last year, Treinen actually threw his sinker less frequently (68.8 percent of the time) than he did in his first two years as a reliever. In trying to diversify his repertoire, he threw more than 30 percent sliders.

Wieters could see that changing.

“You start to realize these [hitters] aren’t seeing him twice in a game. They aren’t seeing him three times in a game. They probably won’t see him three times throughout the span of two months,” Wieters said. “With Blake, he’s got a great slider. He’s got a great change-up, and there may be days when the sinker’s not on that he can maybe go through that lineup without it.”

There may be days like that. But Wieters has directed a version of this movie before. He knows there will be days when Treinen’s sinker is not just the best pitch in his arsenal but the best on that given day in the National League.

“We’ve already been talking about: That’s the pitch that makes him special,” Wieters said. “It’s his sinker. That’s the one.”

There is a blueprint for what the Nationals are trying to do with Treinen. Their catcher helped sketch it out. There are no guarantees the results will be the same. But watch for that 90-something-mph heat, then watch it drop, heavy and hard. And when Wieters throws the ball back to Treinen for the next pitch, expect the same again.

For more by Barry Svrulga, visit washingtonpost.com/svrluga.