(CNN)Colin Kaepernick trained with the Las Vegas Raiders this week, signaling a potential comeback in the NFL, according to US media reports.
Kaepernick worked out for the Raiders on Wednesday, NFL Network Insider Ian Rapoport reported.
The 34-year-old -- who drew controversy for kneeling during the national anthem when he was a San Francisco 49er, protesting racial injustices and police brutality in the US -- has not been involved in an NFL game in more than five years.
In March 2017, Kaepernick opted out of his 49ers contract and became a free agent. No NFL team signed him. In October 2017, he filed his grievance case against the NFL, alleging that teams were colluding to deny him a job.
The quarterback settled a collusion grievance case against the NFL, along with his former 49ers teammate Eric Reid, in 2019.
Raiders owner Mark Davis said he would welcome Kaepernick "with open arms" provided the team's coaches and general manager were on board.
"He deserves every chance in the world to become a quarterback in the National Football League," Davis told NBC Sports.
Kaepernick has expressed his desire to play in the NFL time and time again -- even signaling he would sign with a team as a backup.
"Yeah. I know I have to find my way back in," Kaepernick said in an interview on the "I AM ATHLETE" YouTube channel.
"So, yeah, if I have to come in as a backup that's fine, but that's not where I'm staying. And when I prove that I'm a starter, I want to be able to step on the field as such. I just need that opportunity to walk through the door."
CNN has contacted Kaepernick's representation and the Raiders for comment.