Dario Saric's last-second swat on Pau Gasol paced the second day of basketball in Rio, which included a record showing from USA's women.
Croatia announced itself as a potential Olympic medal contender in men's basketball on Sunday with one fell swoop of Dario Saric's outstretched arm.
Saric - a 22-year-old power forward one month removed from signing with the NBA's Philadelphia 76ers - blocked Pau Gasol's would-be buzzer-beater as time expired to seal a 72-70 win over Spain, dealing the two-time silver medallists a crushing blow to open their Rio tournament.
Croatia took off on a 7-0 run to grab the lead down the stretch when Saric - a lottery pick in the 2014 NBA Draft - rose to the occasion and rejected Gasol as his potential game-tying lay-up fluttered the opposite direction. Gasol, playing in his fourth Olympics, scored a game-high 26 points.
Saric's block highlighted a men's Group B opener that included Lithuania's 82-76 victory over host Brazil and a 94-66 Argentina rout of Nigeria.
On the women's side, the heavily favoured United States squad opened its attempt at a sixth consecutive gold medal with a 121-56 romp of Senegal, setting Olympic records for points scored in a game, margin of victory and assists. France, Australia and Spain also secured tournament-opening victories.
HIGHLIGHT OF THE DAY
Saric managed but one block in his five-point, five-assist, seven-rebound performance in Croatia's win, and he made it count.
MVP OF THE DAY
Australia star Liz Cambage was 9 of 16 from the field as her double-double (22 points, 11 rebounds) helped hold off Turkey, whose top three scorers combined for 52 points in the 61-56 defeat.
QUOTES OF THE DAY
Saric told reporters his game-clinching block on Gasol "was like cherry on the cake."
"We need to keep trust in us in our team-mates. We need to stay together like we always did. I think what happened today will keep us much more together. We cannot make mistakes anymore. The next game against Brazil will be even harder than today. We need to watch some video, talk to the coach and see what we can do better because today was not our best game, but we were so close to winning." - Spain coach Nikola Mirotic of his team's ability to recover.
Group A men's play continues on Monday with preliminary games between the United States and Venezuela, Australia and Serbia, and France and China. USA also play on the women's side in a match-up with Spain on short rest. Other women's Group B preliminary games include Canada against Serbia, Japan facing Brazil and Senegal tackling China.