More from Woj:

The Knicks did include Barrett in trade proposals for Mitchell, sources said, which is why the process to complete the extension extended several additional weeks. Barrett was a staple of several different trade variations discussed, but hurdles remained on Monday about the total of unprotected first-round picks in the deal and the inclusion of Knicks guard Quentin Grimes, sources said.

Nevertheless, the Jazz greatly valued Barrett as part of any Mitchell deal with New York, and a deal without him would require the Knicks to relinquish far more draft assets than they've shown a willingness to do, sources said.

Once the Knicks committed to Barrett's extension, management became resigned to the fact that there's a much more difficult path to an offseason deal to acquire Mitchell. Nevertheless, neither Utah or New York is ruling out restarting the talks before the start of training camps in late September, sources said.

The sides have been discussing a trade on and off since early July. Out of the 179 players in NBA history who've had the Poison Pill provision, only one -- Devin Harris in 2008 -- was moved.

For trade purposes, "The Poison Pill" is computed with a formula that would make the Knicks' outgoing salary on a trade at $10.9 million but require the incoming salary for a team acquiring him to be $26.2 million. The restriction will be lifted on July 1.

For Barrett to be included in a trade to the Jazz, the Knicks would need to find a third team with salary cap space to redirect Evan Fournier's $37 million contract.

The Jazz aren't seriously engaged elsewhere on a Mitchell deal now, sources said, which makes real the possibility that he could still be on the roster for the start of late September training camp.