(John McDonnell / The Washington Post)

In today’s Post, we had a story on Jordan Zimmermann’s star-turn start to the season. The most illustrative figure may be this: Since the start of 2012, only one starting pitcher – Clayton Kershaw – has a better ERA than Zimmermann’s 2.61. He has flown under the radar, his preferred style, but it may not stay that way for long.

One crucial point from the story is how negotiations for a contract extension between Zimmermann and the Nationals have gone. The sides spoke this winter, according to both Zimmermann and his agent, Mark Pieper of SFX Baseball. In the spring, Zimmermann said, he informed the Nationals he wanted to wait until after the season to talk extension and agreed to a one-year, $5.35 million deal in arbitration. But he remained interested in a fair deal down the road.

“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.”

Pieper agreed with Zimmermann’s stance. He also said he and the Nationals have a strong working relationship, and indicated their conversations about Zimmermann have productive.

“We’ve talked about it with the Nationals,” Pieper said. “Obviously, the Nationals recognize how good he is. We’ve had conversations about it but we’ve not done anything long-term and I can’t tell you whether there would be or not be in the future. But we have an open dialogue with them. We’ve done a lot of business together, our firm and that team. There’s no lines in the sand or hard line rules about that kind of stuff. It’s an open dialogue.

“At this point in the game, we’ve not done anything long-term. I can’t say that there ever would be or wouldn’t be but we’ll see how it goes. During the season, probably best left to focus on what he’s doing and continue to try and win some games for this team. And we’ll see what the future holds in the offseason.”

The issue of Zimmermann’s contract is not pressing because of his status – he cannot become a free agent until after the 2015 season. It is pressing because of the growing, league-wide trend of teams signing young stars to contract extensions before free agency looms.

Once players reach the season prior to becoming eligible for free agency, they tend to ride it out and gauge their value on the open market. If not, their contracts typically look like monster free agent deals, anyway – last year, with only one season left between him and free agency, Giants right-hander Matt Cain signed a six-year, $127.5 million extension.

The Nationals and Zimmermann could take a while to reach a deal. Contract extensions are built on comparable cases, and his individual circumstances generate few comps.

Zimmermann is a Super Two player, meaning he accumulated enough service time before three full seasons that he qualified for arbitration a year early. Rather than three rounds of arbitration eligibility, Zimmermann earned four, two of which he has already gone through.

The distinction matters. Zimmermann reaching arbitration a year earlier than most raises the starting point of his salary, which would serve as the basis of any extension talks. There are really no recent Super Two players with four-plus years of service who signed extensions that could be a model for a long-term deal.

Remove the Super Two distinction, and a few more examples fit. In January, the Rangers signed left-hander Matt Harrison to a five-year, $55 million extension when he had two seasons remaining before free agency. At that point, Harrison had a 110 ERA+ (ERA adjusted for ballpark effects, with 100 as league average) over 624 1/3 innings with a 48-30 record.

Zimmmermann has flatly been better, and is only improving with overpowering start to 2013. In his career, Zimmermann has a 122 ERA+ over 553 innings and a 32-28 record. Barring a setback, Zimmermann will finish with better performance more innings than Harrison had when he sat at the negotiating table this winter.

The last time a pitcher with between four and five years of service time signed a long-term extension came in the winter before the 2010 season. In a matter of days, Justin Verlander and Felix Hernandez signed five-year deals worth $80 million and $78 million.

By that point in his career, Verlander had already thrown 840 innings with a 115 ERA+, and he was coming off a third-place finish in the Cy Young vote. Hernandez had thrown 905 innings – which is just insane – with a 125 ERA+ and had just finished as the Cy Young runner-up.

If Zimmermann signs a deal after this season, it will likely fall closer to the Verlander-Hernandez end of the spectrum, especially if his season continues its course toward all-star status and Cy Young contention. Zimmermann will not be as accomplished as those two aces. But the financial structure of the game has changed in three years. New television deals have driven salaries skyward. The price of free agency has increased, which has put more pressure on teams to prevent their homegrown stars from reaching it.

Zimmermann’s performance is only driving his price higher. There will be one other complicating factor in his case. In 2011, the Nationals voluntarily shut down Zimmermann after 161 1/3 innings, costing him about five or six starts and about 30-35 innings. Should that sliver of performance count?

Zimmermann’s agent could argue he should get credit, because the team prevented him from throwing those innings, even if they did so with the intent of protecting his arm in the wake of Tommy John surgery. The Nationals would surely counter that if Zimmermann didn’t pitch those innings, then they can’t be counted toward his career track record.

You wonder if that’s one reason the sides went to the brink of an arbitration hearing this spring. You also wonder what effect Stephen Strasburg’s shutdown will have on the tenor of negotiations when it comes his turn for arbitration.

In any event, the subject of Zimmermann’s contract will play itself out following this season. Zimmermann likes it in Washington, and the Nationals want him to be part of their long-range plans. As Zimmermann has shown for the past three years, there is no reason why they shouldn’t.