NEW YORK -- Alex Rodriguez's fight to overturn the longest drug-related suspension given to a MLB player entered its next phase on Monday when his lawyers filed suit in U.S. District Court alleging that arbitrator Fredric Horowitz, who handed down a 162-game ban on Saturday, was biased in his ruling.

The suit seeks to vacate Horowitz's ruling, based on the arbitrator's "manifest disregard for the law," his "evident partiality," and refusal "to entertain evidence that was pertinent and material to the outcome."

The complaint calls the 162-game ban "wholly unjustifiable" and alleges that Horowitz ignored the stipulation of baseball's Joint Drug Agreement, which calls for a 50-game ban for a first-time drug offense.

"He ignored the clear disciplinary action of the JDA," the complaint reads, referring to the arbitrator. "Accordingly, the Arbitration Award is not legitimate as it does not draw its essence from the JDA or [C]BA."

Horowitz explained in his ruling that he factored in "Rodriguez'[s] obstruction of MLB's investigation'' and "the prolonged time period ... with which he used or possessed the three Prohibited Substances.''

"While the length of the suspension may be unprecedented for a MLB player,'' Horowitz wrote, "so is the misconduct he committed.''

Rodriguez's 42-page complaint names Major League Baseball and the Major League Baseball Players Association as defendants and includes among its exhibits Horowitz's written ruling on A-Rod's appeal.