Doug Fister joined the Washington Nationals this winter after a trade with the Detroit Tigers. A left-handed batter and right-handed thrower, Fister will be an asset to this season’s starting pitcher lineup. (Whitney Leaming/The Washington Post)

Doug Fister has always wanted to know how things worked. As a kid, he built cities out of Lincoln Logs and tinkered with Matchbox cars. Tired of her son dismantling her functioning appliances, Jan Fister let him fiddle with a broken vacuum cleaner. Without the benefit of a manual — to Jan’s great surprise — Fister fixed it.

In high school, Fister could take apart the front end of his father’s 1970 Monte Carlo and put it back together without instructions. In the minor leagues, Fister worked construction in the offseasons for extra income. He can afford a builder now, but for fun this winter he remodeled his bathroom.

“He’s got a mind that is just always going,” Larry Fister said. “He likes a challenge.”

The challenge before Fister, 30, as the Washington Nationals prepare to open official workouts for pitchers and catchers Saturday, is to convince his new team he really is not too good to be true. When the Nationals shipped utility man Steve Lombardozzi, lefty reliever Ian Krol and pitching prospect Robbie Ray to Detroit, they received in return a 6-foot-8 workhorse who throws a sinkerball that plunges as if made of cement.

They also got the son of a former Merced, Calif., fire captain and SWAT team member; a playoff competitor who stared down the eventual world champs after taking a line drive off the head; an athlete who played high school hoops and runs 10 miles between starts; and a burgeoning star who behaves like a regular guy.

“He’s going to sign something like a five-year, $70 million contract one day,” said Mike Batesole, Fister’s coach at Fresno State. “I’m pretty sure he’s going to have $70 million worth of jeans and T-shirts and a pickup truck with stock rims on it.”

Fister is the product, foremost, of generations of firefighters and cops. Fister’s paternal great-great-grandfather was a firefighter in the 1800s, his great-grandfather was a county sheriff in Nevada and his grandfather served in the Air Force. His uncle was on the police force, a sniper first and then a detective.

After playing football at Fresno State, Larry Fister worked as a police officer for 12 years, spending part of his career on the SWAT team, knocking down doors on raids. He rose to the rank of captain during 20 years with the Merced Fire Department.

Fister would practice shooting alongside his dad and flip pancakes at fundraising breakfasts for the fire department. He watched how the men bonded — if one firefighter needed his roof redone, the entire department spent Saturday at his house. Fister studied to be an elementary school teacher in college, but he figures he would have gone into law enforcement or firefighting if not for baseball.

“It’s amazing how many different areas it really has affected in my life,” Fister said. “From one, being a man, to two, baseball, to three, how camaraderie works. Brotherhood in firefighting and law enforcement is so big. And it’s a big thing here as a team. It’s a brotherhood. We’re basically a family here. That’s something I’ve witnessed for a long time, and it’s something I try to emulate.”

His father’s work also gave Fister a unique appreciation of what pressure really means. With his inquisitive mind, Fister asked his father how he stayed calm, how he didn’t get scared busting into a home.

“You will do under pressure what you’ve been trained to do,” Larry Fister said. “I don’t care if it’s law enforcement, a secretary answering the phone or a pitcher on the mound. Your mind is going to revert back to what you were trained to do.”

From his father and his uncle, Fister also learned the importance of staying in the moment. He dismissed bad pitches or home runs allowed as something no longer in his control. In the playoffs the past three seasons, Fister posted a 2.98 ERA over eight games. Under pressure, he did what he was trained to do.

“You can always tell when you get in the playoffs what kind of guy you got,” Tigers pitching coach Jeff Jones said. “He was always great in the playoffs.”

Fister’s career could have gone down a different path. The San Francisco Giants drafted him out of Merced Community College in the 49th round — as a first baseman. On the night the Nationals traded for Fister, he called his father, took a deep breath and said, “Well, I’m on the move again.” After he explained he was headed to Washington, Fister took another long breath. “It’s a new team and a new start,” he said, “but at least I get to swing the bat again.”

Fister had always told his parents he wanted to play Division I baseball, and so he spurned the Giants for Fresno State. He chose to stay in Fresno for his senior year even after the Yankees drafted him in the sixth round following his junior season. He finally became a professional when the Seattle Mariners took him in the seventh round in 2006.

It was not a smooth path to the majors. In 2008, the year before he debuted in the majors, Fister went 6-14 with a 5.43 ERA at Class AA. His failure convinced him to lean on his strengths — command and movement — and not try to please coaches with strikeouts and velocity. He succeeds with a sinker that induces bushels of groundballs even as it travels in the mid-80s.

“The difference came when he realized he had to stay within himself,” Larry Fister said. “He can throw it harder than he does right now.”

On Friday morning, Fister walked into the Nationals’ clubhouse for the first time. He sat in a row of lockers among Stephen Strasburg, Gio Gonzalez and Jordan Zimmermann, the kind of rotation mates who may overshadow him. He doesn’t mind.

“From Day 1, my father’s always instilled in me not to speak about it, just go out there and work hard and let your actions show what you’re all about,” Fister said. “That’s my mentality and the mentality that I try to take out to the ballpark every day.”

More from the Nationals:

Nationals Journal: Roenicke gets minor league deal

Nationals Journal: Davis says elbow strain ‘not that bad’

Nationals Journal: No restrictions for Garcia

Nationals Journal: Clippard relieved to avoid arbitration

Nationals Journal: Lobaton is ‘Ice Cream Man’