Jordan Zimmermann became the National League's first eight-game winner as Washington beat the Phillies, 5-2, at Nationals Park on May 24. (John McDonnell/THE WASHINGTON POST)

Above all, Jordan Zimmermann desires control. He will dictate the terms of confrontation, regardless of the scale or the opponent: hitters in the batter’s box, management during contract talks or the stardom onrushing as he blooms into one of the most dominant pitchers in baseball.

Zimmermann will not throw a tailing fastball on purpose, because he prefers the precision of his straight four-seamer. He told Washington Nationals officials this spring that any talks about a contract extension will have to wait until after the season. He will not consider appeals for, say, a local car commercial, even after – especially after – fellow introvert Stephen Strasburg filmed one for Toyota.

“I would never do that,” Zimmermann said last week, leaning back in his chair in the visitors’ clubhouse at San Francisco’s AT&T Park. “He said that those commercials take like six hours. I’m like, ‘There ain’t no way I’m hanging out and saying the same [stuff] for six hours.’”

Zimmermann, 27, has only made his resistance against celebrity more difficult this year. Through the Nationals’ disappointing first third of the season, he has been the shining constant. Zimmermann will make his way to the mound Wednesday night in Baltimore – a slow walk, always – at 8-2 with a 1.71 ERA, a challenger to Strasburg as the Nationals’ best pitcher and one of the best starters in the majors.

Zimmermann’s first 10 starts have served less as a breakout than a continuation of a progression. Since the start of 2012, only Los Angeles Dodgers ace Clayton Kershaw, at 2.31, has a lower ERA than Zimmermann’s 2.61 among full-time starters.

The Post Sports Live crew discusses what would happen to the Nationals’ lineup if Bryce Harper keeps suffering minor injuries. (Post Sports Live)

“I don’t know if I’ve gone up a level,” Zimmermann said. “I’m doing the same things as last year, you know? I’m not giving up quite as many runs, and I’m getting a lot more run support.”

Zimmermann feels no different one year further removed from 2009 elbow ligament replacement surgery. Surely, a .235 batting average against him on balls in play, likely a sign of good fortune, has helped. Zimmermann, after years of trying, added a change-up to a mid-90s fastball, a bullying slider and a 12-to-6 curveball.

“He keeps hitters on their heels,” Nationals right-hander Dan Haren said. “With his stuff, he can really attack hitters and keep his pitch count down. Stuff-wise, it’s about as good as it gets.”

Even if Zimmermann throws it only a few times per game, the mere existence of his change-up makes an already nasty repertoire more menacing. “Maybe the only thing is hitters know I have a halfway decent change-up, and they got that in the back of their mind,” Zimmermann said. “That’s about the only thing I can think of.”

Pitching coach Steve McCatty said Zimmermann’s biggest improvement is his increased aggressiveness with off-speed pitches – starting off at-bats with them, throwing them when he’s behind and throwing them for strikes.

Zimmermann fills up the strike zone better than most. He ranks tied for fifth in the majors with a 68 percent strike percentage, the same rate as last season. His groundball percentage has shot up from 43 percent last season to 51 percent this season. If he gives up a hit, he attacks the next batter with the same strong will.

“He just doesn’t give,” McCatty said. “I don’t know how he was brought up. I know he shot a deer and killed a deer when he was a kid. A lot of [upper-Midwest] kids have done that, but I don’t know if they have the same mind-set he does.”

Zimmermann has led the Nationals’ staff through hard-charging example. After Strasburg imploded four starts ago against the Chicago Cubs, he studied Zimmermann to improve his demeanor. In three unflappable outings since, Strasburg has allowed three earned runs in 23 innings. Zimmermann said he never spoke with Strasburg about it, but Strasburg cited Zimmermann’s influence after the first start of his dominating run.

“I don’t think you really need to talk about mound presence,” Zimmermann said. “You see a guy, how they act. You just have to make the change yourself. I think I’ve told him a couple times in the past, ‘You just got to be the same person, no matter what’s going on, what’s happening. You can’t show signs of weakness out there, or the other team, the hitters, they know they got you right where they want you. Even if it is going bad, you still got to be the same person.’ ”

‘General toughness’

Zimmermann’s agent, Mark Pieper, first witnessed Zimmermann’s resolve at Division III Wisconsin-Stevens Point in 2007 during the pitcher’s junior season. It was March. Snow covered the ground. Fans and scouts wore ski masks, gloves and scarves. “And he was out there in a short-sleeve shirt grinding away like it was no big deal,” Pieper said.

“It comes naturally,” Zimmermann said. “I’ve never been one to smile and have a good time out there, or make it look like I’m having a good time. I’m not one to shrug my shoulders when there’s a bad play. I just try to stay even-keeled the whole time.”

Added Pieper: “There’s a general toughness to him. I think it shows. Just like all the other guys in the major leagues who are extremely talented, there’s an inner drive and a competitiveness about him. He wants to be the best. He may not talk about it.”

Even though Zimmermann’s statistics rank him among the game’s best, he has received little widespread recognition. He has never been an all-star or won an end-of-year award. He also hasn’t pitched as much as other top pitchers because of 2009 Tommy John surgery, rehabilitation during most of 2010 and a subsequent shutdown in 2011. Last season, even though he produced 24 quality starts in his 32 appearances, he lacked run support and went 12-8. More wins have brought more notice. They have not changed Zimmermann’s demeanor.

“If you can get Jordan Zimmermann to brag about himself, good luck,” Pieper said. “I haven’t been able to do that, nor will I ever.”

The Nationals have tried, too. He does not mind chatting with local reporters, but when possible he declines interview requests from national television outlets. Zimmermann also resists entreaties from Washington’s public relations staff to open a Twitter account. “I just like to fly under the radar,” he said.

Contract issues?

Zimmermann is a star, even if he will not act like one, and the trend around baseball has seen teams lock up their best young players with contract extensions. The Nationals and Pieper have discussed a deal to keep Zimmermann in Washington long term, but the talks never materialized into the basis for a contract.

Zimmermann said he would listen to offers from the Nationals. But he seemed content to hold out for free agency, which he would be eligible for after the 2015 season.

“We talked a little bit in spring training,” Zimmermann said. “My agent and I said once the season starts, we’re going to wait until after the season. Hopefully, we’ll maybe spring something up at the end of the season or going into next season or something.

“I’d be interested, see what they have to say. At the end of the day, it’s got to be the right deal for me. I’m not just going to take a deal that’s team friendly. It’s got to be fair.”

The Nationals, then, will soon learn what major league batters have felt all season. When they stare at Zimmermann, they see a face giving away nothing, a man making them react to him, a pitcher in full command.