We're still waiting for official word, but ESPN's Jim Bowden reports that the Nationals are trading Jason Marquis to the Diamondbacks, who are sending prospect Zach Walters to the Nationals.

Marquis will obviously slide right into Arizona's rotation, taking the slot held for most of the season by Barry Enright, recently demoted to Class AAA. With the D'backs' other four starters all featuring sub-4.00 ERAs, the club should have a consistent (if unspectacular) rotation as they try to catch the Giants down the stretch.

Zach Walters has moved up quickly. Just a ninth-round draft pick just one year ago, Walters batted .302/.338/.440 last summer in the short-season Northwest League, and has fared even better this season in the Class-A Midwest League. Previously a shortstop, Walters has been converted into a utility infielder, seeing time at second base and third base as well as short.

He's been compared to Geoff Blum, which seems strange for a 21-year-old in his second pro season. But there you go.