Hearts' first-team coach Gary Locke admits Driver's future is uncertain as the winger prepares to discuss a move to the Major League Soccer club.
The MLS transfer window is open ahead of the start of the season in the USA and 25-year-old could make an immediate move.
Locke told Hearts TV: "There's a possibility that Andrew could be leaving. We are still waiting to find out what the situation is.
"He has been a fantastic lad to work with but we are not 100% sure what's happening at the moment.
"If he stays, great, if he goes, we wish him all the best. But at this moment in time it's still pretty much up in the air."
Oldham-born Driver is out of contract in the summer and seemed certain to move on given the club's need to cut their wage budget.
The former England Under-21 international, who can still play for Scotland under the five-year schooling rule, has made more than 150 appearances for Hearts since coming through the youth ranks.
Hearts placed a £4million price tag on Driver in summer 2009 when Burnley attempted to sign the player for a second successive summer, while Coventry and FC Twente were also linked with moves for the player.
But a series of injuries hampered his progress, although he has been fit without interruption for more than 12 months now, and Hearts will have to accept a much smaller fee from the Americans.