A USA vs. USA final in the most interesting tennis Olympic event -- mixed doubles -- was decided on a dramatic, enlongated tiebreaker.

Jack Sock and Bethanie Mattek-Sands toppled Venus Williams and Rajeev Ram, winning the tiebreaker 10-7 (7-6), and taking the ultimate match two sets to one. Mattek-Sands and Sock rallied after falling in the first set, then came back from a three-game deficit in the third set.

Mattek-Sands and Sock rallied on Sunday to nab gold. USATSI

For Williams, one of the best tennis players of her generation, it could mean her final Olympic competition. She's won four gold medals, but also shockingly lost earlier at these Games in women's doubles alongside her sister, Serena.

Sock took bronze a few days ago, placing third in men's doubles alongside Steve Johnson.

Mixed doubles has made a resurgence at the Olympics. It was part of the London program in 2012 (the United States' team of Lisa Raymond and Mike Bryan took bronze), but prior to that it wasn't part of an Olympiad since 1924. Mixed-gender events are so rare, it's great to see something like tennis embrace this.

Golf, which returned to the Olympic docket for the first time since 1904, could increase its intrigue factor and offer a unique, team scoring system if it were to go to a mixed-team format for the 2020 Games in Tokyo.