In a blow to the NFL, an arbitrator has ruled that Colin Kaepernick’s collusion case against the league can proceed because he has produced sufficient evidence that the league and its owners colluded to keep the free-agent quarterback off the field.

The ruling by Stephen B. Burbank, an arbitrator who was appointed by the league and the NFL Players Association, said that Kaepernick’s lawyers had unearthed enough evidence in the past year for the case to proceed to a full hearing. After months of depositions and document searches, the lawyers will be able to question league officials, owners and others in trial-like format.

The decision was revealed by Mark Geragos, Kaepernick’s lawyer.

Kaepernick filed a grievance against the NFL in October accusing the owners of conspiring to not offer him a new contract because of his decision to protest during the playing of the national anthem. In August 2016, Kaepernick was the first player to kneel during the anthem to raise awareness of police brutality and other forms of social injustice.

Dozens of other players ended up joining Kaepernick, creating a schism among fans, sponsors and owners. Last season, President Donald Trump attacked the league for not penalizing players who did not stand for the anthem. In May, the league tightened its policy to force players to stand for the anthem, instead of just suggesting they stand.

Since he became a free agent in March 2017, Kaepernick has not been invited to work out for a team, or been offered a new contract. Some team officials have quietly suggested that Kaepernick’s best years were behind him, while others said they did not want to sign him to play as a backup. Kaepernick, who is now 30, played six years with the San Francisco 49ers and led them to the Super Bowl in his second season.

John Elway, the former Denver Broncos quarterback who is now general manager of the team, muddied the waters further when he told the NFL Network that he did not sign Kaepernick because the player had once been offered a contract and turned it down.

Elway, though, did not say that he offered Kaepernick a contract in 2016, when he was set to receive $12 million from the 49ers, and months before he first protested. Kaepernick said no because he would have had to take a pay cut to join the Broncos. Elway said that he did not sign Kaepernick when he became a free agent the following year even though he might have accepted far less than $12 million to play in Denver.

Elway did not say explicitly that he shunned Kaepernick because he protested during the anthem. But Kaepernick’s lawyers contend that the quarterback was still talented enough to play in the NFL, and that he was willing to be a backup if needed. The NFL has shunned Kaepernick because of his political views and his decision to protest during the anthem, his legal team has argued.

During discovery, Kaepernick’s lawyers have requested hundreds of pages of documents from the league office and teams. It has also questioned, in closed-door sessions, owners of the Dallas Cowboys, the New England Patriots and several other teams, as well as league officials including Commissioner Roger Goodell and Troy Vincent, the executive vice president of football operations.

If Kaepernick wins his case in a full hearing, he would be eligible to receive the money he might have received if he were signed as a free agent. The damages would be tripled.

Eric Reid, who was one of the first players to protest with Kaepernick when both of them were on the 49ers, also has filed a grievance against the league. Reid became a free agent this offseason, and though considered one of the best safeties on the market, has not yet been signed by a team.