Uruguay dominated but had to settle for a 1-1 draw against Saudi Arabia in the sweltering heat of Miami on Monday to leave an intriguing Group H wide open.
The stalemate came hours after one of the biggest shocks in World Cup history when European champions Spain were held 0-0 by debutants Cape Verde in the same group.
After the first round of games in the pool all four teams have one point.
Defender Abdulelah al-Amri gave the Saudis a surprise lead near the end of the first half only for Uruguay's second-half pressure to pay off with 10 minutes left through Maxi Araujo.
Uruguay, World Cup winners in 1930 and 1950, saw their arrival in the United States from Mexico delayed by a snag with the paperwork for their plane.
Marcelo Bielsa's side though had the first chance of the game when Araujo stung the palms of Saudi goalkeeper Mohammed al-Owais after five minutes.
In evening temperatures of more than 30C and energy-sapping humidity, both teams struggled to create much in front of goal early on.
Just after the half-hour mark the Saudi stopper was called into action again to parry away a diving header from close range by Federico Vinas.
The Saudis, who stunned eventual champions Argentina 2-1 to start their campaign at the Qatar 2022 World Cup, looked to hit their opponents on the break.
They had their first real opportunity shortly before half-time when Amri forced Fernando Muslera to palm away his fizzing shot.
Four minutes before the break the defender did score, reacting fastest to poke home from close range after Muslera spilled a header from a corner.
After a toothless first period, Bielsa had seen enough, dragging off defender Matias Vina and anonymous former Liverpool striker Darwin Nunez.
Winger Agustin Canobbio and left-sided Juan Manuel Sanabria were introduced.
The double substitution sparked Uruguay -- who surprisingly did not play a single World Cup warm-up game -- into action in the second half.
Saudi coach Georgios Donis, brought in just two months before the tournament, saw his team retreat farther and farther back.
On the hour Manchester United midfielder Manuel Ugarte pinged the ball against the foot of the Saudi post from well outside the box.
The pressure finally told late on when Owais made a mess of a routine stop and Araujo gobbled up the rebound.
There looked to be only one winner after that, but Saudi Arabia just about held on for a vital point.