Oct 07, 2009 2:39 PM EST

Scott Boras has served former client Gary Sheffield with a $600,000 lawsuit.

Boras filed the suit under seal in Manhattan federal court last week.

The two have been feuding since Sheffield dumped Boras just before he signed a $39 million contract with the Yankees, from whom he played from 2004 to 2006. But Boras has claimed Sheffield still owes him money.

Via New York Post