Colin Kaepernick (center) and Eric Reid (right) attend the third round of the U.S. Open tennis tournament at the USTA Billie Jean King National Tennis Center on Friday in New York. (Greg Allen/Invision/AP)

Serena Williams lauded the efforts of controversial NFL players Colin Kaepernick and Eric Reid after the pair drew substantial applause when introduced during her match against sister Venus Williams at the U.S. Open in New York on Friday.

“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,” Williams said. She said she didn’t notice the two as they were introduced because she was focused on the match, but visited with both players afterward.

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.

Read more from The Post:

Bob Costas and NBC are talking about ending a decades-long partnership

A Korean soccer superstar is one win away from avoiding lengthy military service

Aaron Rodgers didn’t dress like the NFL’s highest-paid player. (But there’s a reason.)

As Adrian Peterson chases history, the smart money is on history