"When I was there, he was playing at a really, really high level," Smith said Wednesday, according to Jeff Fedotin of Yahoo Sports. "Crazy to think that he's not playing."
Kaepernick and Smith played two years together with the San Francisco 49ers before San Francisco traded Smith to the Chiefs prior to the 2013 season.
Many have argued league owners are effectively blackballing Kaepernick from the NFL as a result of his national anthem protest last year and social activism.
Seattle Seahawks defensive end Michael Bennett said in June he thinks "race and politics" are part of the reason Kaepernick remains without a team.
"Obviously, there's the elephant in the room why Kaepernick isn't signed, and most people know why, Bennett said, per ESPN.com's Sheil Kapadia. "I've said this several times, and I'm not afraid to say it: I think race and politics in sports is something people don't want to hear about, nor do people want to be a part of."
Kaepernick met with the Seahawks in May, but Seattle decided against signing him, with head coach Pete Carroll telling reporters Kaepernick deserved an opportunity to start—something he wouldn't be afforded with the Seahawks.
The 29-year-old was also recently linked with a move to the Baltimore Ravens. ESPN's Dianna Russini reported Ravens head coach John Harbaugh and general manager Ozzie Newsome were both behind the signing but that team owner Steve Bisciotti had reservations.
The Ravens posted a statement on Twitter in which Newsome denied Bisciotti had instructed the front office not to sign Kaepernick.