Johnson, who is not expected to appear in tomorrow's meeting with Leeds at Elland Road, regardless of any outcome of today's contract negotiations, has attracted the attention of several clubs and is already believed to have turned down Colchester United.
Johnson signed a new two-year deal at Sixfields last season and is under contract until 2009, but the amount of interest in him had made his departure from Northampton highly likely during the January transfer window.
The ex-Cambridge player has scored five times this season and played in all but one of the Cobblers' matches, and United were hoping to push the transfer closer to completition during talks this afternoon.