A league source told CBSSports.com Thursday the Celtics and Clippers were informed days go that Boston coach Doc Rivers could not be part of any trade under league trade rules and the collective bargaining agreement.
Reports had the Clippers reaching out to reopen trade talks with the Celtics Wednesday, with scenarios likely including Rivers, Celtics veteran Kevin Garnett, and the Clippers' DeAndre Jordan and draft picks.
The source told CBSSports.com Rivers also could not be a part of a separate trade that does not involve players.
NBA commissioner David Stern said Thursday the only incentives or assets that are permitted in NBA trades are player contracts, draft picks and cash.
Stern told ESPN radio in New York:
"The teams are aware that the collective bargaining agreement doesn't authorize trades involving coaches' contracts.
"The teams know that," Stern said. "It has been confirmed to them. ... It can't be gotten around by breaking it up into two transactions."
Stern said -- and a person familiar with the communication between the league and the teams confirmed -- that there is no separating the two deals at this point because it is obvious all the pieces are part of the same negotiation.
"If you think those, at this point -- having been all over the media for the last week -- are separate transactions ... I have a bridge that I would very much enjoy selling to you," Stern said.
The concern from the league's perspective is that Rivers' value and salary cannot be accounted for under cap rules and thus cannot be included in a trade involving players -- nor can it be negotiated as a contingency to a trade.
"It would be an issue of getting around the cap," a league source said.
Reports that Clippers potential free agent Chris Paul wanted the team to obtain Rivers as head coach will likely be tied to Stern vetoing Paul being traded by the then-New Orleans Hornets to the Lakers in 2011.