Here’s a 22nd century tennis trivia question: “Who was Roger Federer’s last opponent?”

Trick answer. There were two: Jack Sock and Frances Tiafoe.

Sock and Tiafoe, both Americans, are definitely the supporting actors in Friday night’s Federer-centric farewell production. But they pose a real threat to Federer going out on a high note.

Sock, in particular, has played a lot more doubles in recent years than Federer or his superstar partner, Rafael Nadal, who have long focused almost exclusively on singles.

Sock, 29, has a glittering 205-96 career record in doubles and has been ranked as high as No. 2 in the world. He recently won the title in Washington, D.C., with partner Nick Kyrgios and just helped the United States Davis Cup team advance to the quarterfinals by partnering with Rajeev Ram to win two crucial matches.

Federer and Nadal have both won gold medals at the Olympics in men’s doubles. Sock’s gold came in mixed doubles in 2016 with Bethanie Mattek-Sands. But unlike Federer or Nadal, Sock has won Grand Slam doubles titles: three in men’s doubles and one in mixed doubles.

Sock has a big serve, an imposing forehand with an extreme grip and fabulous touch and reflexes at the net. Despite his solid frame and sometimes sleepy gaze, he also is very quick, which means that he and the speedy Tiafoe will be able to close a lot of gaps in a hurry tonight against Federer and Nadal.

But though Tiafoe, 24, just broke through to reach the semifinals in singles this month at the U.S. Open, he could be the weak link in this match. He has yet to win a doubles title on tour and has a losing career record of 23-39.

Tiafoe, an extrovert with a flashy game, does like a big occasion and an electric crowd, however, as he proved again in New York this year. He certainly seemed relaxed in the run-up.

“I’m just excited to play two up-and-comers tomorrow,” Tiafoe joked on Thursday.

Sock already has played those up-and-comers in doubles at the Laver Cup, losing with partner Sam Querrey in 2017 to Federer and Nadal in their first-ever official match together.

For Tiafoe, given the circumstances, it will be a once-in-a-lifetime experience.