Rio takeaways: Monica Puig's gold medal just part of the story

Puig proving 'nothing is impossible' (0:41)

Monica Puig talks about winning gold in the Rio Olympics for women's singles and is glad to remind the people of Puerto Rico that "nothing is impossible." (0:41)

These days, you're never quite sure what you're going to get from 34-year-old Serena Williams -- and women's tennis is more compelling (not to mention competitive) because of it.

After sailing through her first two matches at the Olympic Tennis Centre in Rio de Janeiro, Serena was stopped in the third round by Elina Svitolina, and the draw opened up dramatically -- to the extent that the No. 34-ranked woman, Monica Puig, vaulted into the gold-medal match.

Those who believe Olympic rings are meaningless to today's thoroughly professional players might want to reconsider that take. The emotions displayed in and around that final match against Angelique Kerber underlined just what a special event the Olympics can be. With nine days of sterling tennis in the rearview mirror, here are five fleeting takeaways from the women's event:

1. Monica Puig was a (startling) revelation

The 22-year-old from San Juan is the first person, male or female, to win an Olympic gold medal representing Puerto Rico. She stared down Kerber, the reigning Australian Open champion, in a powerful finals performance, 6-4, 4-6, 6-1. In fact, Puig took down three Grand Slam champions en route (also Garbine Muguruza and Petra Kvitova). Going forward, believe it or not, that achievement might resonate greater than the gold itself.

2. Serena Williams is showing some nerve

And this is not in a good way. For several years, Serena, who turns 35 in September, has floated nicely above the fray when most 30-somethings normally start to lose their command. At the time, what we saw at the US Open last year in a semifinal loss to Roberta Vinci looked like a collapse under the pressure of chasing a calendar-year Grand Slam. In retrospect, it might have been the beginning of the end of her complete dominance of the sport. Losing to Svitolina, a woman who had never beaten her, is typical of where Serena finds herself these days. She will likely win more majors, but it's going to get progressively more difficult.

3. Madison Keys is still a work in progress

The 21-year-old American is widely thought to be a future No. 1 player, but she experienced some growing pains in Rio. Keys hits the ball huge, but Kerber is that rare player who can defend those big strokes. Keys was 0-for-10 in the crucible of break points on Kerber's serve and must find a way to master those pivotal moments with something other than bash and brawn.

4. Venus finds redemption

While the 36-year-old failed to escape the first round in singles and went down early with her sister in doubles, mixed doubles was another story. Playing with Rajeev Ram in an attempt for her record fifth gold medal, Venus fell to Jack Sock and Bethanie Mattek-Sands in the championship match. Still, a silver was her fifth Olympic medal in tennis, equaling Kathleen McKane of Great Britain, who won a gold, two silvers and two bronzes in the 1920s.

5. Bethanie Mattek-Sands is money

You have to love the spark this 31-year-old American can still create. Mattek-Sands can now add an Olympic gold medal to her already impressive resume. She and Sock came back to beat Venus and Ram 6-7 (3), 6-1, 10-7. Mattek-Sands had previously won two Grand Slam women's doubles titles (in 2015, with Lucie Safarova) and two mixed-doubles crowns, with Horia Tecau in 2012 and Mike Bryan in 2015.