Wishart has concerns for the future of Gretna's playing staff
Gretna are likely to be able to field a team against Celtic on Sunday after players decided against strike action.
However, it will be a much weakened side as a dozen squad members have indicated an unwillingness to feature unless guarantees can be given.
Players are disappointed that administrator David Elliott could not give assurances that their contracts would be honoured until the summer.
"Players want clarity," said Players' union chief executive Fraser Wishart.
Gretna put a team together to lose 3-0 to Aberdeen at the weekend, despite several first-team regulars refusing to play in the absence of medical insurance.
Staff were this week handed a portion of their unpaid wage bill by the club's administrator.
The sum amounts to 55% of one week's pay, although they are still owed two full weeks plus bonuses.
If it goes ahead, some money will be generated by Sunday's meeting with Celtic, which has been moved to Livingston's Almondvale Stadium because of drainage problems at Motherwell's Fir Park, where Gretna are tenants.
But players could be left in limbo if Gretna go out of business before the end of the season.
Wishart told BBC Sport: "The players are no clearer regarding guarantees about their futures.
"There are a number of players who could get a club at very short notice and there are other guys who are not interesting clubs.
"There are a whole host of different interests, so any decisions taken have to be individual decisions.
"Each person has to look after their own future."
Wishart is also increasingly concerned by the lack of communication from Fifa over the plight of Gretna's playing staff.
World football's governing body has yet to respond to the SFA's requests to give Gretna's players dispensation to move club beyond March.
Players whose contracts are terminated may re-sign for another club with Fifa permission.
But rules also state that no club can sign players after March, which would pose problems for Gretna players should the club go out of business after then.
Gretna's administrators told staff they are free to look for other clubs if they wish.
However, caretaker manager Mick Wadsworth outlined the obstacles involved.
"There's interest from other clubs and I'm sure players and agents are talking to clubs, but we're in abnormal circumstances," Wadsworth told the club's website.
"There is a huge problem with international clearance, cancellation of registration and moving outside the transfer window, so it's not an easy situation and we need guidance."