Cardiff - Wales hooker Ken Owens has branded an expected merger between the Scarlets and Ospreys as the "most challenging situation" of his career as the Ospreys chairman quit over radical proposals to revamp regional rugby.
The British and Irish Lions front-rower is among scores of professional players whose immediate futures are in limbo, with the Welsh Professional Game Board (PRB) thrashing out a way forward in meetings on Tuesday.
A new professional team in north Wales could also be set up, in Welsh rugby's biggest domestic shake-up since the inception of regional sides 16 years ago.
Scarlets hooker Owens, the Welsh Rugby Players' Association chairman, revealed his fears in a candid statement and said players must be consulted.
"As the chairman of the WRPA I am deeply concerned about the situation that the players across the four regions face," said Owens.
"I recognise that this is the most challenging situation that I or arguably any player has faced during our rugby careers."
Wales' PRB comprises representatives from the Welsh Rugby Union, Scarlets, Ospreys, Dragons and Cardiff Blues.
It is understood that the favoured plan is to retain four regional teams, but they would be north Wales, an Ospreys-Scarlets merger, Blues and Dragons.
Any merger would need to establish a home ground, in addition to issues such as the new team's name and kit.
So-called "Project Reset" is being played out against a backdrop of Wales chasing this season's Six Nations title and a possible Grand Slam.
Wales face Scotland at Murrayfield on Saturday, followed by Ireland in Cardiff seven days later. Victories in both games would secure a first Six Nations clean sweep since 2012.
Around half of Wales' matchday 23 for the Scotland clash is likely to comprise Ospreys and Scarlets players.
If a merger goes ahead, players such as Wales captain Alun Wyn Jones, Jonathan Davies, George North, Owens and Leigh Halfpenny would be part of the same regional squad.
The WRU has not commented on Tuesday's planned discussions.
Wales boss Warren Gatland said at a press conference on Tuesday: "It comes down to being able to put enough finances and resources into the game. For me, I would love nothing better than two or three teams challenging in Europe."
The Ospreys announced their chairman, Mike James, had resigned, citing the WRU's "catastrophic mismanagement" of efforts to overhaul the game.
James made his the announcement at the start of Tuesday's board meeting in Cardiff.
"None of us doubt that regional rugby requires restructuring in order to ensure the long-term sustainability of the game," James said in a statement released by the Ospreys.
"The way in which this has been handled, however, is nothing short of chaotic, resulting in a fatal combination of uncertainty, conjecture and insecurity now hanging over regional rugby's future."