10:35pm: A source confirms the existence of the trade negotiations to Marc Stein of ESPN.com, saying that the deal is still in the works. The Suns are seeking only draft picks and short-term contracts, Stein adds (Twitter links).
9:45pm: The Bucks and Suns are in "serious" negotiations about a trade involving Caron Butler, reports Gery Woelfel of the Racine Journal Times. Woelfel tweeted earlier tonight that Milwaukee made a run at Butler before the Clippers traded him to the Suns last month in the same three-way deal in which the Bucks sent J.J. Redick to L.A. The Suns are barred from trading Butler until September 10th if they include another player in the deal, but they can swap him at any time if they send him out by himself. Woelfel says the deal could be consummated by today.
An injury to free agent acquisition Carlos Delfino is fueling Milwaukee's pursuit of an established small forward, Woelfel writes, adding that he's heard rumors that Delfino could miss part of the regular season after undergoing surgery for a fracture in his right foot. Giannis Antetokounmpo and Khris Middleton are the only other small forwards on the roster.
Butler's $8MM expiring contract would put Milwaukee just above the salary cap, so they'll have to send salary out as part of the deal. The Bucks have eight different players capable of playing either power forward or center, so it figures that they'd try to include one of them in a trade. In any case, it's not likely to be a marquee name heading to Phoenix, according to Woelfel, as the Suns are prioritizing assets that can help them in the future over immediate returns. Draft compensation will probably be the jewel of the swap for Phoenix, though that's just my speculation.
Bucks GM John Hammond and new Suns GM Ryan McDonough have been among the most active executives on the trade market this summer. If they strike a deal involving Butler, it would be Milwaukee's fifth trade since the beginning of July, and Phoenix's third. And while few players would welcome a winter in Milwaukee instead of Phoenix, Butler is a native of nearby Racine, Wisconsin, so presumably he'd be on board.