Nobody saw this coming

The field for this fall’s playoffs -- not to mention the rosters of three current division leaders -- might be far different if Josh Byrnes, then Arizona’s general manager, hadn’t approached the New York Yankees’ Brian Cashman with an idea shortly before Thanksgiving in 2009.

What transpired next may have contributed to Byrnes’ firing eight months later. And it no doubt cost Cashman some sleepless nights the next summer. But the three-team, seven-player trade consummated a month later with the Detroit Tigers changed the fortunes of two franchises and set up outfielder Curtis Granderson for one of the greatest seasons in the Yankees’ long and storied history.

“The idea for all clubs when they’re making a deal is to do the best for themselves,” said Jerry Dipoto, Arizona’s vice president for player personnel at the time of the trade and now the team’s head of scouting and player development. “But I think even on paper that one appeared to address [everyone’s] needs. And it’s proven to be better than that.”

The deal sent Granderson from Detroit to the Yankees and right-hander Edwin Jackson from the Tigers to Arizona. The Yankees moved right-hander Ian Kennedy to the Diamondbacks and pitcher Phil Coke and outfielder Austin Jackson to the Tigers. Arizona, which gained two pitchers, also lost two in Max Scherzer and Daniel Schlereth, former first-round draft picks who went to Detroit.

It all started with what must have sounded like a plea to Cashman.

In two years, the Diamondbacks had gone from a 90-win playoff team to a 90-loss last-place team. With staff ace Brandon Webb’s health uncertain -- in fact, he wouldn’t pitch again for Arizona -- Byrnes wanted Kennedy.

In return he could offer ... well, nothing the Yankees wanted. What Cashman needed was a young, athletic outfielder to replace the aging Johnny Damon and the hobbled Hideki Matsui. But Byrnes wouldn’t part with any of his.

The trade was dead before it had taken its first breath.

However, the Tigers revived it. Detroit not only had the guy the Yankees where looking for in Granderson, but the Diamondbacks had the kind of power arms Tigers General Manager Dave Dombrowski collects like trading stamps.

“We had a lot of discussion,” Cashman said. “It did take a long time, a lot of creativity by the people here at this table to pull it off.”

Twenty months later, all that work has proved worth it.

After posting a 9-10 record in his first season for an Arizona team that lost 97 games -- and cost Byrnes his job -- Kennedy has emerged as a Cy Young Award favorite, with a 19-4 record and 2.90 earned-run average for a team that is cruising to a division title.

In Detroit, where the Tigers are closing in on their first division title since 1987, Scherzer is second to Justin Verlander with a career-high 14 wins, Schlereth has made 45 relief appearances, Coke has emerged as a valuable swingman, eating up more than 100 innings, and center fielder Jackson, a minor league player at the time of the trade, has a league-leading 11 triples along with 20 stolen bases.

Granderson is having the best season of all. He leads the majors in runs (126) and is second in runs batted in (109), home runs (38) and extra-base hits (70), and fourth in slugging percentage (.566) while hitting .268, stealing 24 bases and playing a Gold Glove-caliber center field.

In the last 88 years, only Nomar Garciaparra and Granderson among AL players have had at least 30 homers, 20 stolen bases and 10 triples in the same season. Granderson is on pace to become only the fourth player to lead his team in homers and triples in the same season.

That has quieted critics who excoriated Cashman for giving up two big league pitchers and a top prospect for a center fielder who finished the 2010 season with more strikeouts than hits.

The reverberations of the trade have been felt by as many as half a dozen franchises.

The acquisition of Granderson made Damon and Matsui expendable in New York. So Damon went to Detroit, then to Tampa Bay as a free agent, strengthening both teams. Matsui led the Angels in on-base percentage last year and is Oakland’s second-leading run producer this season.

Byrnes, who was fired along with manager A.J. Hinch after starting Arizona’s rebuilding process, is now trying to turn around the San Diego Padres as the team’s head of baseball operations.

Jackson pitched a no-hitter during his four-month stay in Arizona before being traded to the Chicago White Sox for Daniel Hudson, a 16-game winner who has become another key piece in the Diamondbacks’ playoff push.

Six weeks ago, Jackson moved again, this time from Toronto to St. Louis at the center of an 11-player trade that brought the Blue Jays Colby Ramus and Trever Miller.

“Most trades, on some level, work out like that. Just not quite as magnificent as this one’s turned out to be,” Dipoto said. “I’m sure all the people wake up feeling pretty good about that day.”

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kevin.baxter@latimes.com