Serena Williams was the star of the US Open on Friday night as she routed her sister, Venus, but her focus was on another athlete after the big victory -- an athlete who attended her match and got a warm welcome from the Open crowd.

That athlete? Colin Kaepernick.

Accompanied by former San Francisco 49ers teammate Eric Reid, the free agent quarterback brought his niece, Lani, to the Williams sisters' match. And after Serena sealed her win, she decided to pay respects to the ex-Niners, championing their activism on and off the field.

Fresh off an early win in a legal battle against the NFL, who he says colluded to keep him out of the league after he protested social injustice during pre-game national anthems, Kaepernick hasn't taken the field since 2016. Reid, meanwhile, hasn't found a team since leaving the 49ers this offseason and has alleged similar wrongdoing. Amid all of it, Williams said athletes -- and people in general -- should be grateful for the conversations they've started.

"I think every athlete, every human, and definitely every African-American should be completely grateful and honored how Colin and Eric are doing so much more for the greater good, so to say," Williams said, according to the Associated Press. "They really use their platform in ways that is really unfathomable. I feel like they obviously have great respect from a lot of their peers, especially other athletes, people that really are looking for social change."