Jose Fernandez and a passenger killed in his fatal boat crash were both drugged before the incident as part of a robbery scheme ... this according to a lawyer for the ex-MLB star's estate.
Attorney Ralph Fernandez has filed new documents in the wrongful death case brought against the Miami Marlins pitcher -- claiming he was carrying $15,000 in cash in a backpack on the night of the incident ... which made him a target for thieves.
Fernandez claims he and Eduardo Rivero were "unwitting recipients of a spiked drink or a mickey of sorts" in a plot to disorient them and steal the money.