Barnet expect midfielder Dean Sinclair to leave Underhill at the end of the season when his contract expires. The Bees have made a number of offers to Sinclair, 22, in an effort to keep the former Norwich youngster.
But the player's agent is reported to have said that Sinclair will join a new club in the summer.
The Bees will be entitled to a fee for Sinclair, who has started 132 games in three years with the club, with the figure likely to be set by a tribunal.