Stephen Strasburg on his 5-month-old daughter: She rolls over a little bit or she makes a new noise, it’s amazing to see. You don’t want to miss any of it.” (John McDonnell/The Washington Post)

Baseball mattered too much to Stephen Strasburg. He suspects he always knew that, but until this winter he never confessed to himself. He shared the conclusion last week without hesi­ta­tion and with an unbridled smile, as he sat at his locker inside the Washington Nationals’ spring training clubhouse. The grin surfaced once Strasburg talked about his baby daughter, 5 months old, happy and healthy and growing like a weed.

“I would never admit it,” Strasburg said. “But now that I’ve had something that’s more important, and the priority of being a good dad is more important to me, I think looking back, maybe I did put a little too much emphasis on baseball. Maybe it wasn’t my only thing I was worried about. But it was definitely higher up there than I thought it was.”

One week from Monday, on opening day, Strasburg will climb the mound at Citi Field in New York. He will carry with him a carefully revamped approach to the in-season preservation of his right arm, an elbow no longer stifled by a pair of bone chips and, most significantly, an altered perspective.

Strasburg, 25, became a father for the first time this winter. Teammates Ryan Zimmerman and Jordan Zimmermann also welcomed their first-born children, and it had varying effects on their professional outlook. “I can’t golf as much as I used to be able to,” Zimmermann said. “I feel like I’m the same person.” For Strasburg, the difference was profound.

Since Strasburg entered professional baseball under the weight of massive expectation, internal and external, he grappled with his perfectionist tendencies. “It’s always going to be a battle,” Strasburg said. “It’s going to be a process.” When he thinks about his daughter, though, the burden melts. Now he places his most intense focus on something other than baseball.

The Post’s Adam Kilgore discusses how much he expects the offseason acquisitions of starting pitcher Doug Fister and outfielder Nate McLouth to impact the Nationals in 2014. (Post Sports Live/The Washington Post)

“I want to go out there and be successful in this game and help this team win,” Strasburg said. “But that’s not my number one priority now. That’s being the best dad I can be. That’s awesome. It’s amazing how that changes your life. Just the little things. She rolls over a little bit or she makes a new noise, it’s amazing to see. You don’t want to miss any of it.”

Trying to be too perfect

Strasburg’s perfectionism drove him to morph from an out-of-shape high school kid to the best pitching prospect in a generation. At San Diego State, his pitching coach preached to him only winning the game mattered, whether he allowed no runs or eight.

He followed the edict, but dominance came easy in college; there were not many eight-run days. In the majors, against the best hitters in the world, demanding perfection ceased to drive Strasburg and began to consume him.

“I think I got away from that,” Strasburg said. “I slowly got in this habit of trying to go out there and do it all.”

Early last year, errors, bloop hits and missed pitches eroded Strasburg’s confidence and soured his body language. Last summer, after he brooded through a start, pitching coach Steve McCatty ordered him into a room with Zimmermann, one of Strasburg’s closest friends. McCatty asked Strasburg what he aimed to accomplish each start.

“To throw a no-hitter,” he replied.

McCatty turned to Zimmermann. “Do you try to throw a no-hitter?” he asked.

“The way I look at it, I give up a hit an inning on average,” Zimmermann replied. “If they don’t get a hit in the first inning, it’s probably going to come in the second inning.”

McCatty started laughing.

The conversation with McCatty and Zimmermann started to crystallize the problem for Strasburg.

“I think I’m a very visual learner,” Strasburg said. “I kind of play things out in my head a lot, before they happen. I think I’ve struggled in the past when things don’t go according to what I’ve envisioned in my head. That stresses me out, maybe gets me a little out of whack. I’ve been trying to switch the focus and not really worrying about that.”

The stress surfaces in his daily life. Strasburg chuckled as he admitted how irritated traffic makes him. His wife, Rachel, stays calm even in crisis.

“I’ve learned a lot from her, too,” Strasburg said. “If I’m in the car by myself, I’m pretty heated. If she’s in there, I’m like, ‘All right, just relax.’

“We’re very opposite. She’s very easy-going. I need structure. The whole routine, starting and everything, it’s got to be the same every time. That’s where I feel like I’m trying to be willing to adjust, be willing to change a little easier and not get out of whack.”

Nationals teammates and confidants have noticed a difference in Strasburg this spring. He stands taller on the mound, in full command. He asks coaches questions with confidence, secure but not stubborn in his approach. He hungers to be better, not to be perfect. He continued the process he started last year. More so, teammates believe, as fatherhood helped him relax.

“He’s a more mature guy than he was a couple years back,” General Manager Mike Rizzo said. “I think he’s more comfortable in this environment. He’s just more comfortable with himself.”

A new comfort zone

Strasburg’s comfort may prove crucial to his health. Last season, after starts that did not meet his standard, he retreated to the bullpen to solve what he perceived as mechanical problems. Between starts, he would play long-toss and pitch off flat ground. He fired as many 60 pitches during some bullpen sessions.

By the end of the season, the Nationals skipped two of his starts after he copped to tightness in his forearm. He started on the season’s final weekend and never complained of any pain. In November, he learned what those mechanical problems really were: He had developed two bone chips in his elbow, and he needed surgery to remove them.

“I didn’t even know there was anything wrong with him until I read he had surgery,” Zimmermann said. “I was like, ‘What the heck?’”

The need for a procedure surprised Strasburg, too. He assumed it had only been inflammation, typical soreness at the end of the season. The surgeon showed Strasburg two bone chips that measured two centimeters each. “Wow,” he thought.

“They looked like two little eggs,” Strasburg said.

The second operation of his major league career led Strasburg to reevaluate his routine. This winter, he played catch and pitched at the same high school field as Kansas City Royals ace James Shields, one of baseball’s most reliable workhorses.

“He was the one who kind of reached out to help me,” Strasburg said. “Which was really cool. Because I’m kind of guy that doesn’t want to be bothering people.”

Shields told Strasburg to be mindful of every throw he made between starts. By the end of the season, Shields told him, all those throws accumulate. He could prevent wear if he trusted his arm and his mechanics. One bad start did not require an overhaul.

The pitchers Strasburg most admires throw 200 innings annually, and he listened to every word. Strasburg vowed to play catch less and to limit bullpen sessions to 25 pitches.

“I wasn’t able to make every start I should have last year, and the year before I got shut down,” Strasburg said. “I think I want to take a better effort and just save my bullets for out there in the game.”

By the end of the winter, Shields and Strasburg threw bullpen sessions side by side. More than his pure stuff, Strasburg’s eagerness to learn and the measured seriousness he brought to his work struck Shields. But the stuff struck him, too. Shields joked one day that he would walk off the mound so he didn’t have to compare his pitches to Strasburg’s.

“He was really, really impressive in his bullpens,” Shields said. “Way more impressive than I’ll be in mine.”

Strasburg made his impression with a new-and-improved arm. Fighting his elbow last year forced the ball to the outside or inside of the plate. He would inadvertently cut a fastball or change-up and think, “God, why is it doing that?” He would overcompensate and mistakenly fire a fastball at a hitter’s head. He could not extend his arm perfectly straight or push his fingers into his shoulder when he flexed his biceps.

Now, he can do both. The few degrees of angle make all the difference. Extension and flexibility returned. When he releases a pitch, the ball spins exactly how he wants. He locates without effort. He added a slider to his repertoire.

“It feels so much better,” Strasburg said. “I’m not trying to force a fastball away with my body. It just kind of happens.”

Strasburg will enter his fifth major league season at the height of his immense powers. It all seems perfect. Inevitably, it will not remain that way. Strasburg has come to accept that, even to embrace it. When he leaves the park, he can leave baseball behind, knowing his favorite part of being a dad awaits.

“I think it’s just coming home and making her laugh,” Strasburg said. “That’s the coolest thing. When they start to think you’re funny, then it’s over. Because you just want to make them laugh all the time.”

He sat inside a clubhouse, dressed in baseball pants and a workout shirt. A few minutes later, Strasburg would pull on his jersey and head outside for practice. Another smile spread across his face. It was clear what mattered more to him, what the coolest thing really was.