By Chris Mortensen and Adam Schefter
ESPN.com

When is a proposal not a proposal? When the NFL and the NFL Players Association are involved.According to sources familiar with the talks, last week's negotiations between the NFLPA and the NFL broke off when the union characterized their documents as an "illustration" that NFL officials believed represented a proposal for revenue sharing between owners and players.

When the NFLPA characterized documents labeled "NFLPA Proposal" as something other than a collective bargaining proposal, the NFL ended the session, a source familiar with the talks said. League representatives then met outside the room, and returned only to abort the negotiations -- without immediately rescheduling any talks, the source added.

"As often happens in collective bargaining, the parties reached a point where there was a fundamental difference on a critical issue that was not going to be reconciled that day," said NFL spokesman Greg Aiello. "The discussions were adjourned to permit both parties to assess their positions and consider how to move the process forward. Far from abandoning the process, in the first four days after the Super Bowl, we have had two meetings of our labor executive committee and negotiating team, a conference call with all 32 clubs, and a meeting with the union."

The day after negotiations broke down, NFL Commissioner Roger Goodell convened a conference call with the owners of the 32 NFL teams and reported the developments of the previous day. A person familiar with that call said there was complete unanimity among the owners.

Despite the aborted Wednesday session, dialogue has continued between the two sides through smaller working groups as well as communication between Goodell and NFLPA executive director DeMaurice Smith. One player source said it is expected both sides will meet this week, as previously scheduled, and a management source did not refute that suggestion.

But there is a growing discord and mistrust between the two sides. Management was irritated by Smith's decision to release the owners' counter-proposal on a rookie wage scale to players and player agents, as opposed to offering a response directly to management. Even the choice of descriptive words were a source of irritation.

Whereas Smith noted that renegotiations or extensions of rookie contracts were "banned" until after the third year, a management official said the proposal "allows" for those renegotiations or extensions after the third year. Regardless, the intent and meaning are the same.

One person connected to the NFLPA said NFL owners were continuing to be "unreasonable," which accounted for the disintegration of last week's meeting.

Now, there are knowledgeable sources that previously were optimistic that CBA negotiations would not result in any lost games next year that are growing increasingly pessimistic. One source said last week's flare up was symbolic and illuminated the schism between the two sides. Now, there is a general feeling that some or all of the 2011 season may be at risk, though there is plenty of time for the two sides to continue talking and trying to bridge their vast differences.

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Chris Mortensen is ESPN's senior NFL analyst. Adam Schefter is ESPN.com's NFL Insider.