The players were two of the most visible to demonstrate during the national anthem to protest police brutality and economic inequality. Both are now free agents.
“They really use their platform in ways that is really unfathomable,” Williams added. “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.”
Kaepernick smiled for fans and Reid raised a fist as they were introduced and shown on the big screen at the Billie Jean King National Tennis Center.
Kaepernick last appeared in a regular season game at the close of 2016, the year in which he gained notoriety for kneeling during the national anthem. He has gone unsigned by NFL teams since and lodged a legal complaint alleging franchise owners have conspired to keep him out of the league.
Reid played for San Francisco in 2017, but has also been unable to find a new team and filed his own legal grievance.
Serena Williams defeated Venus Williams, 6-1, 6-2. She faces Kaia Kanepi of Estonia on Sunday in the round of 16.
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