So the Arizona Diamondbacks, already entrenched atop the National League West, which they have led since April 6, swing a deal.

And not just any deal: It isn't very often that the Major League home run co-leader changes teams, but Adam Dunn and his 32 homers are presently on their way from Cincinnati to the desert.

So this goes down 11 days on the other side of the Trading "Deadline." So how can this be happening?

Rather routine, actually -- or, as routine as anything governed by necessary bureaucratic guidelines can be.

The July 31 cutoff, remember, is for "non-waiver trades," the end only of baseball's open market. Thereafter, as a precondition of deals, any rostered players potentially involved must first be exposed on a waiver list.

All teams regularly receive a comprehensive waiver list, and can claim listed players in reverse order of the standings, which is what Arizona did.

Considering the D-backs' position, obviously a lot of teams passed before their turn came around. But affecting the decision to claim, or not, are a lot of mitigating circumstances -- besides the obvious one of need.

Foremost among the factors is contract status: Dunn is still owed about $4 million on his 2008 salary of $13 million; a team making a successful claim could be saddled with that debt, so it is not a move to be taken lightly.

Waiver lists are a part of daily Major League life. It is team's lure when angling for possible transactions.

When a claim is made, the claimed player's team can do one of three things: Simply withdraw the player's name, let the claiming team have him -- or attempt to negotiate a derivative trade with the claiming team.

The latter is what Cincinnati general manager Walt Jocketty and his Arizona counterpart, Josh Byrnes, did on Monday morning.

Recently, there was also an example of a waiver-triggered negotiation that did not lead to a trade. After the Boston Red Sox had put in a claim for San Diego outfielder Brian Giles, the teams began discussing a prospective deal that eventually collapsed.

Giles' decision not to waive no-trade rights which he held was believed to have dead-ended that transaction.

The post-Deadline market is clearly different. It is non-competitive, for one thing: Prior to the Deadline, teams with expendable players can pit suitors against each other, hoping to drive up the prize; afterwards, it is a one-to-one process.

Yet it's a process that often has yielded dramatic results in the past, and may do so again before the month is out. (Waiver deals go down prior to the Sept. 1 cutoff date for postseason eligibility.)

Obvious targets to keep an eye on are those who were already in play prior to July 31, but stayed put.

Those include San Diego's sage right-hander, Greg Maddux, Braves outfielder Mark Kotsay, Mariners left-hander Jarrod Washburn, Colorado lefty closer Brian Fuentes and Toronto catcher Gregg Zaun.

"Other names on the August counter are such veterans with postseason experience as Indians right-hander Paul Byrd, Reds relievers David Weathers and Jeremy Affeldt, and Detroit outfielder Gary Sheffield."

With teams eager to get an edge in the many tight races around the Majors, further deals are sure to happen.

On a similar playing field, the revolving door spun particularly fervently last August. No fewer than a dozen deals were swung, and the players included Mark Sweeney (Giants to Dodgers), Wily Mo Pena (Red Sox to Nationals), Craig Monroe (Tigers to Cubs) and Steve Trachsel (Orioles to Cubs).

OK, perhaps significant shifts at the time, but no one who figures to have a long shelf life on future Hall of Fame ballots.

A retrospective does yield a more illustrious list of August movers who shook up their new teams:

• Jamie Moyer: He went from the Mariners to the Phillies, whose rotation he still anchors, on Aug. 19, 2006.

• Shawn Green: The postseason-bound Mets acquired him from the D-backs on Aug. 22, 2006.

• Larry Walker: The Rockies icon was acquired by the Cardinals on Aug. 4, 2004.

• Jason Bay: One of the principals of this summer's Deadline-day activity left the Padres along with Oliver Perez for the Pirates, in exchange for Giles, on Aug. 26, 2003.

• Rickey Henderson: The imminent Hall of Fame outfielder was dealt by the Padres to the Angels on Aug. 13, 1997.

• Lee Smith: The record-holder until recently for career saves was acquired by the Yankees from the Cardinals on Aug. 31, 1993.

• Pedro Guerrero: The four-time All-Star was acquired from the Dodgers by the Cardinals in exchange for right-hander John Tudor, runner-up for the NL Cy Young Award three years earlier, on Aug. 16, 1988.

• John Smoltz for Doyle Alexander: One of the most consequential deals in history -- a guy who has 210 wins and 154 saves for another guy who ushered the Tigers into the playoffs by going 9-0 the rest of that season -- went down between Atlanta and Detroit on Aug. 12, 1987.

Just a sampler because, despite the annual focus on the non-waiver Trade Deadline, baseball's market hardly shutters up after July 31.