Williams made the comments during an interview with Time magazine. The 23-time Grand Slam winner bought into the Dolphins' franchise with her sister Venus Williams in 2009. The superstar sisters are just a few of the celebrities involved with the team, behind managing general partner Stephen Ross.
Those celebrities also include Fergie and Marc Anthony.
Kaepernick, 30, hasn't taken an NFL snap since his last season in 2016 with the San Francisco 49ers. He posted a 1-10 record as a starter that season, but inspired a movement against police brutality and racial inequality that still takes place today -- players kneeling during the national anthem before football games.
Although Kaepernick remains unsigned and has a pending collusion case against the league, which he filed in October, Williams told Time that he is "happy with what he's doing." She's met the football player twice.
Kaepernick has been ultra active in the activism since his last snap, raising $1 million to fight oppression globally through education and social activism. He also donated the proceeds from his jersey sales in 2016 to organizations working in oppressed communities.
Williams doesn't think an NFL team will hire him, but says Kaepernick could win the big game. Kaepernick has already been close to accomplishing the feat. He helped the 49ers reach the grand stage in 2013, before losing to the Baltimore Ravens by three points in Super Bowl XLVII.
Kaepernick completed 16-of-28 passes for 302 yards, a touchdown and an interception in the loss. He also ran for 62 yards and another score against the Ravens.
"He'd have so much to prove," Williams said of Kaepernick's potential comeback. "I would. I can't imagine he would be any different. 'Man, I'm about to show out. Y'all gonna see stuff you've never seen before.'"
The tennis star donated $10,000 to Imagine LA, matching Kaepernick's donation in January, as part of his $1 million donation push.