AP Photo/Vadim Ghirda

American tennis players Madison Keys and Sloane Stephens attended the women's gymnastics preliminaries Sunday, and, in Keys' words, they were "freaking out" over the competitors so much that other fans asked, "Are you family?"

As Keys recalled Monday, they replied: "We feel like it, but we're not. They don't know us."

Keys is a professional athlete who is one of the best on the planet at her sport - ranked in the top 10 in the world and a Grand Slam semifinalist last year. Yet she is in awe of the physical feats of her counterparts in other disciplines at the Rio Olympics.

She met a race walker the other day, for instance.

"She can do a 6-mile mile - I can't run that fast," Keys marveled.

The 21-year-old Keys is one of those Olympic fans who adores watching the sappy profiles of athletes before their events. She'll be crying by the time the subject steps up to the starting line, thinking, "Oh, my God, I love you. I never met you but I know you."

Keys and Stephens were sending video from the gymnastics to teammate Serena Williams on Sunday, making the four-time gold medalist - who had two matches that day - quite jealous. Stephens lost in the first round, while the seventh-seeded Keys rallied from down 5-3 in the third-set tiebreaker to beat Kristina Mladenovic 7-5, 6-7 (4), 7-6 (5) in 3 hours, 14 minutes in the second round Monday.