An NFL appeals officer rejected Ezekiel Elliott’s appeal on Tuesday and upheld the six-game suspension for the Dallas Cowboys running back.

But a longer legal battle looks to be ahead after the NFL Players' Association filed a request for a temporary restraining order against any ruling that would subject Elliott to a suspension.

"We are extremely disappointed with Mr. Henderson's inability to navigate through league politics, and follow the evidence, and most importantly, his conscious," Elliotts' attorneys wrote in a statement following the ruling. "The evidence that Mr. Elliott and his team presented on appeal clearly demonstrated that Mr. Elliott was the victim of a conspiracy orchestrated by the National Football League and its officers to keep exonerating evidence from the decision-makers, including the advisors and Roger Goodell. The only just decision was to overturn the suspension in its entirety.

"Mr. Elliott is looking forward to having his day in federal court where the playing field will be level and the NFL will have to answer for its unfair and unjust practices."

Henderson heard Elliott’s case over two and a half days in New York City, listening to testimony from the running back and his representatives, who included lawyer Jeffrey Kessler, who previously helped Tom Brady and Adrian Peterson in their cases against the NFL.

In the NFLPA's filing, the union claimed that "there was a League-orchestrated conspiracy by senior NFL executives .... to hide critical information -- which would completely exonerate Elliott." The NFLPA also contested that the appeal process was "fundamentally unfair."

The NFL spent a year investigating allegations of domestic violence made against Elliott by his former girlfriend in July 2016. Citing extensive digital evidence as well as the testimony of Elliott’s accuser and medical experts who examined photographs of her injuries, the NFL levied its six-game ban on Aug. 11. That punishment is in line with the personal conduct policy the NFL updated in 2014 in the wake of former Baltimore Ravens running back Ray Rice's domestic violence case.

Unlike the substance abuse policies, the personal conduct policy was not collectively bargained with the NFL Players Association. Last year a federal appeals court upheld Brady’s four-game suspension for his alleged role in the Deflategate scandal, with the ruling largely made on the basis of NFL Commissioner Roger Goodell having broad disciplinary power.

Elliott was never arrested or charged and has maintained his innocence. The prosecutor in Columbus, Ohio, who declined to pursue charges told NFL investigators he "generally believed" Elliott's accuser with respect to all of the alleged incidents, but told USA Sports last October he felt he had insufficient evidence to pursue any charge.

Follow Lindsay H. Jones on Twitter @bylindsayhjones.