Zack Greinke fired his agent, John Courtright, the day after Courtright rejected the Nationals’ offer of a $100 million contract extension. “I could definitely see,” Greinke said, “how it looks a little weird.” (Morry Gash/AP)

Decision time was approaching fast for Zack Greinke. It was mid-December, and the Kansas City Royals were preparing to honor his request for a trade, and the Washington Nationals were among the teams working to acquire him, and an offer of a $100 million contract extension had been made to Greinke’s agent by the Nationals, and at that critical juncture, with the baseball world waiting to see what he would do, Greinke . . . fired his agent.

Within another 48 or so hours, everything would be resolved. Greinke, the 2009 American League Cy Young winner, would quickly hire a new agent, and on Dec. 18, would waive his no-trade rights — without the enticement of a contract extension — to accept a trade to the Milwaukee Brewers.

In Washington, however, folks in the Nationals’ front office were left wondering: What just happened? More specifically, they wondered: Why did Greinke fire his agent, John Courtright, the day after Courtright rejected their contract-extension offer? Surely, that wasn’t a coincidence.

Presented with that question on Tuesday, as he sat in the Brewers’ spring-training clubhouse, an earbud stuck in one ear and attached at the other end to an iPad, Greinke declined to discuss specifics (“If the Nationals want answers, I’ll talk to them,” he said), but he acknowledged the sequence of events made it appear as if he was upset at Courtright for turning down the offer. (Courtright, meantime, did not return a telephone message seeking comment.)

“I could definitely see,” Greinke said, “how it looks a little weird.”

Greinke, however, insisted the decision to reject the Nationals was his own — and was not about the money, but rather his desire, at age 27 and after seven years of losing in Kansas City, to go to a team with a chance to win right now.

“It wouldn’t have gotten as far as it did [with the Nationals] if it wasn’t appealing,” Greinke said. “The one thing I couldn’t get over was the fact that, here I was trying to get out of Kansas City because the team wasn’t good. Not saying [the Nationals] don’t have a chance, but I was trying to get to a team that was looking really good at the moment. And I believe [the Nationals] will be good eventually.”

Much of what Greinke came to know about the Nationals and their ambitions he learned in early December during a clandestine meeting with high-ranking team officials in Orlando during baseball’s winter meetings.

“What got us talking seriously was the fact their owner wants to win really, really bad,” Greinke said, referring to Nationals managing principal owner Theodore Lerner, with whom Greinke met in person. “They convinced me they were really trying, and I believe them. My whole family liked the possibility of going there. I respect everything about the Nationals. And I’m not a guy who goes around saying that about every team.”

Five weeks into his first spring training with the Brewers, Greinke is mostly a spectator, having suffered a cracked rib in early March while playing in a pick-up basketball game. The injury is likely to sideline him for the first few weeks of the regular season.

But the injury has also given the Brewers a chance to get to know a pitcher who has been described as introverted, complicated and sensitive, and who has had a well-publicized battle with social anxiety disorder that at one point made him quit baseball altogether.

“I find him very interesting,” Brewers General Manager Doug Melvin said. “I’ve talked to him some. I told him I wished I could do what he does, which is to filter out all the unnecessary things and focus on what you have to do. He’s a very focused guy.”

Meantime, a continent away, the Nationals are preparing to make do with a starting rotation lacking the No. 1 starter the front office sought, but failed to land, all winter. In addition to Greinke, they tried to trade for former Tampa Bay Rays right-hander Matt Garza, whom the Rays traded instead to the Chicago Cubs.

In their face-to-face meeting with Greinke in Orlando — held at an off-site hotel, so that the media would not be aware of Greinke’s presence — the Nationals pointed to their recent signing of free agent right fielder Jayson Werth, to a seven-year, $126 million contract, as proof of their commitment to constructing a winner in Washington.

“The Nationals got Jayson Werth, and if they got me to come there, then free agents and other players start thinking, ‘Hey, Washington’s getting some players,’ ” Greinke said. “I think that was a big reason they wanted me — to convince other players to come.”

For the Nationals, the cost of acquiring Greinke would have been steep — not only in terms of money, but in talent. The Nationals indicated to the Royals that they were willing to part with Jordan Zimmermann, one of their top young pitchers, and discussed other names such as reliever Drew Storen and second baseman Danny Espinosa — two other young, low-cost players at the core of the team’s building-from-within model — as potential pieces of the package, according to sources familiar with those discussions.

That, too, factored into Greinke’s equation, he said, when it came time to decide where to go.

“The Nationals are trying to build a winner,” Greinke said, “and if I’m going to go there, I didn’t really want them to trade away the players they were going to build around. That hurts their team.”

When it was suggested to Greinke that perhaps his path will intersect with that of the Nationals another time — Greinke’s current contract expires after the 2012 season, roughly the time the Nationals expect to become legitimate contenders — he did not shoot down the notion.

“Maybe it works out better that the deal [with Washington] didn’t go through,” Greinke said. “In two years I might be a free agent, and then they get to keep the players [who would have been] in the trade. And some of those guys could end up being key players for them.”