If it had not before, the rest of the world is now sending a message to defending champions the United States men's basketball that it will not be a cakewalk this time, despite triumphing 94-91 to remain perfect at Rio 2016.
For the second time in three days, USA found themselves sweating in the fourth quarter of an Olympic matchup as Serbia rallied from 18 points down to get within one possession of going to overtime against the reigning gold medallists.
One would have assumed after getting their first real taste of competition against Australia on Wednesday that the Americans would look to send a message to the rest of the world they are still the overwhelming favourites. And they did at first, leading 23-5 at one point in the first quarter.
But sloppy half-court play on both offense and defense from USA helped the quick-cutting Serbians dissect the Americans' defense and had the entire world on upset watch, before making it four wins from as many games in Group A.
Elsewhere in pool play, Australia easily defeated China 93-68 without Andrew Bogut, and France came up with their second win in a row by beating Venezuela 96-56.
USA's women took care of business against Canada with an 81-51 win. Spain handled Senegal 97-43 and Serbia beat China 80-72.
Serbia's Miroslav Raduljica came up with 18 big points in the near upset, putting the moves on USA big men before fouling out in the fourth quarter.
MVP OF THE DAY
USA came away with the win, but the most impressive player on the court on Friday was Serbia's Nikola Jovic. The Denver Nuggets forward scored 25 points off the bench to help push the Americans.
"I think it's great that we're getting challenged. Whatever the case is, we got to do a better job. These teams are figuring out ways to execute down the stretch. I think the biggest key is that this team has been playing for a while. This is a new group for us, regardless of the talent. This is a new group, so we're still learning, we're still trying to figure out each other. As good as we are offensively, defensively is where we got to really man up," - Paul George on USA being challenged.
"I'm really proud of how we played in the last 35 minutes, but still we are missing two minutes on Australia and five minutes against USA so I hope that we're going to get better and understand that we have to start playing for 40 minutes," - Serbia coach Aleksandar Djordjevic on Friday's close call against USA.
Saturday resumes pool play for Group B in men's competition. Croatia will take on Nigeria, Spain will face undefeated Lithuania and Argentina meet Brazil. On the women's side, Australia tackle Belarus, Japan clash with France and Turkey will go up against Brazil.