Shocker Sunday in Rio shows that Olympics are unlike any event on tour

When the Olympic tennis event began on Saturday morning, more than a few fans claimed that it felt “like any other week” on tour. The reaction was understandable. The players, the format, the scoring system: They were the same as they would be at any other dual-gender Masters event. The only thing Rio seemed to have that, say, Toronto didn’t, were those five rings plastered behind both baselines.

Now we know, if we didn’t before: Never underestimate the power of those rings. By the end of the weekend, it was clear how much they still mean, even to the tennis pros whose careers aren’t entirely geared toward them. After two Games, in Beijing and London, where the world’s best players rose to the occasion, Rio feels like it’s going to be a throwback to the chaotic, upset-filled Olympic tennis events of old, to those strange days when people named Nicolas Massu, Marc Rosset, Li Ting and Sun Tiantian walked away with gold around their necks.

Two days into the 2016 Games, the top two seeds in the men’s doubles—France’s Nicolas Mahut and Pierre-Hugues Herbert and Great Britain’s Andy and Jamie Murray—are gone. So are the No. 4 and No. 5 seeds in the women’s singles, Agnieszka Radwanska and Venus Williams. And to top it off, the No. 1 seeds in the men's singles and the women's doubles, Novak Djokovic and Venus and Serena Williams, were sent packing on Sunday night.

Along the way, the Rio crowd has made it clear that it will be a wild card in the proceedings. While these multinational fans tend to arrive late, they came out in force for the first two night sessions, and their loyalty seems to be up for grabs. Their support for Kirsten Flipkens on Saturday night was a big part of her eventual comeback win over Venus. No wonder Flipkens bent down and kissed the rings when it was over.

But while that result was a surprise, it paled in comparison to what happened on Sunday.

Late in the afternoon, Venus and Serena, three-time doubles gold medalists, lost for the first time in their Olympic careers, to Barbora Strycova and Lucie Safarova. Then, just as we had processed that information, Juan Martin del Potro came along to blow our minds again, handing Djokovic just his fifth loss of 2016 and his first on hard courts in a completed match.

Which was the bigger surprise? In truth, while Djokovic is far and away the best player in the world, and the Williams sisters may be the best doubles team of all time, neither of these results were impossibilities. The Games will always be something of a crapshoot for the best players. Even in an Olympic year, the tours' rhythms still follow the four majors, and the top pros, those creatures of extreme habit, aren’t used to targeting an event that isn’t scheduled with them in mind and is held at a completely new and unfamiliar venue.

So we probably should have seen Venus and Serena’s Sunday struggles coming. Safarova is a former Top 10 player, and Strycova is a fearless all-courter, just what you need in doubles. Put that together with the fact that Venus was sick, and the two sisters had hardly played with each other over the last two years, and you had the makings for trouble. That trouble quickly turned into a perfect storm.

Venus’ reactions were slow at the start; to compensate, Serena tried to be more aggressive than normal, but that only took her out of her own game. On at least three occasions, Serena moved too early on a poach and left a wide open court for the Czechs to hit into behind her. At the same time, Strycova, sensing opportunity, was a happy dervish at the net. In the past, the Williams sisters have always been the faster, stronger, more domineering team. This time it was Strycova, the smallest woman on the court, who continually beat them to the punch, and who ended one point by emphatically drilling a ball between Venus’ legs. It was a sad end to what had to be a crushingly disappointing weekend for the Olympic-loving Venus.

Almost as soon as the Czechs' upset registered, though, it was all but forgotten in the wake of Del Potro’s 7-6 (4), 7-6 (2) win over Djokovic. This was Olympic tennis at its finest, a big-hitting, slow-moving—both guys took their time between points—war of heavy artillery, played in front of an audience that brought a World Cup-level energy to the arena.

Unfortunately for Djokovic, it was clear from the beginning that this was your father’s Del Potro. The old, unstoppable, tank-like power was back in his game, and once he has you in his sights, it's tough to escape. Since his comeback began in March, I’ve wondered whether Delpo’s forehand is actually better, out of necessity, than it was during his early-20s prime. With his bad left wrist still hampering his two-handed backhand, he has needed his biggest weapon to be even bigger. Rarely has it been more effective—jaw-droppingly effective—than it was against Djokovic on Sunday night. Del Potro finished with 41 winners, and brought the crowd to its feet over and over with his forehand onslaught. At the same time, his backhand was steadier and more solid than it has been all year; his depth from that side allowed him to run around and set up for his forehand.

While Delpo was throwing caution to the wind, Djokovic was staying conservative—too conservative. The key to beating the Argentine is to move him relentlessly, but Djokovic couldn’t find the angles and the corners he needed to do that; the slow court that had seemed to favor Djokovic only gave Del Potro more time to unload. Djokovic couldn’t make any inroads on Del Potro’s serve, and he played rattled tennis in the tiebreakers. Twice in the second one, Djokovic approached down the line to Delpo’s forehand; twice he watched as Delpo thumped a cannon-like pass down the line for a winner. Those two gut punches took the final wind out of Djokovic’s sails.

Djokovic, whose left wrist was taped, fought hard in this one. But his 2016 Olympics singles quest would end the same way his 2012 Olympics one did, with a defeat to Del Potro that left him short of a medal. He gave his conqueror a hug at the net and told him he deserved to win. Then both men cried as they walked off court.

If you didn’t know by then, you knew it when you saw those reactions: This isn’t like any other week on tour.