What you need to know:
- The Iranians sent their thousands of fans wild when Ramin Rezaeian clipped in a second goal on the counter-attack.
- Brazil's team camp announced that superstar forward Neymar would miss the side's next game against Switzerland after he suffered ankle ligament damage in their opening 2-0 win against Serbia.
Argentina will seek to save their World Cup skins in Qatar on Saturday when Lionel Messi and his teammates face Mexico in a match they cannot afford to lose.
A stunning 2-1 defeat to Saudi Arabia has left Argentina, who arrived in Doha on a 36-match unbeaten run and as one of the overall favourites, in a precarious position.
The Argentines said they will draw on memories of superstar Diego Maradona, their 1986 World Cup-winning captain who died two years ago this week, to inspire them against the Mexicans.
"We keep him in mind. He was a very important person in world football, and not just for us Argentines," said Inter Milan forward Lautaro Martinez.
"Today is a sad day for everyone and hopefully tomorrow we can give happiness."
The Argentines know they cannot afford a repeat of their opening match in Group C.
"It was difficult but we're a united group, a strong group that knows what we want, we know about our opponents, we've already overcome many things," said Martinez, who twice had a goal ruled out for offside against the Saudis.
The surprising Saudis have a chance to prove they are no flash in the pan when they face Poland and Robert Lewandowski, the prolific striker who is still looking for the first World Cup goal of his career.
The Barcelona forward missed a penalty in the goalless draw against Mexico.
In other games on Saturday, defending champions France could book their place in the last 16 if they beat Denmark at Stadium 974, which incorporates shipping containers in its design.
The French lost defender Lucas Hernandez to injury in their opening 4-1 win against Australia, adding to a list of absences headed by Ballon d'Or winner Karim Benzema who limped out of the World Cup before a ball was kicked.
Australia face another rough ride against a robust Tunisian side.
Hosts Qatar go out
In Friday's action, host nation Qatar crashed out of their own World Cup following a second straight defeat.
Qatar lost 3-1 to Senegal and became the first team to be knocked out of this World Cup after the Netherlands and Ecuador drew 1-1 in the other Group A game to seal their fate.
Asian champions Qatar had high hopes coming into the tournament but became only the second home team to crash out in the group stage, after South Africa in 2010.
Goals from Boulaye Dia, Famara Diedhiou and Bamba Dieng were enough to give African champions Senegal the win.
Mohammed Muntari scored Qatar's only World Cup goal so far in a deeply disappointing debut on football's biggest stage -- it is the first time a World Cup host nation has gone out after just two games.
"We would like to say we're very sorry to the supporters, to the country," said Qatar defender Tarek Salman.
"We have made them feel bad about losing two games in a row in the World Cup."
Senegal must now beat Ecuador to advance to the knockout phase while the Qataris face the Dutch.
An uninspired England missed the chance to wrap up qualification for the knockout phase following a 0-0 draw with the United States.
After thumping Iran 6-2 in their opening match, England rarely troubled a well-organised USA unit and were booed off at full-time.
"A draw isn't the end of the world for us, it puts us in a great position in the group," England captain Harry Kane said.
England need only avoid a four-goal defeat by neighbours Wales on Tuesday to advance and know a victory will send them through as group winners.
Earlier, Iran scored twice deep into stoppage time to stun Wales 2-0 and breathe new life into a World Cup campaign overshadowed by mass anti-government protests at home.
The Iranian players sang the national anthem before their win over Wales, having opted to stay silent in their opener in Qatar in an apparent gesture of support for the demonstrators.
They were worthy winners against a team reduced to 10 men late in the match.
Iran, who would have been eliminated if they had lost, punished Gareth Bale's Wales in the eighth minute of injury time when substitute Rouzbeh Cheshmi smashed home.
The Iranians sent their thousands of fans wild when Ramin Rezaeian clipped in a second goal on the counter-attack.
Brazil's team camp announced that superstar forward Neymar would miss the side's next game against Switzerland after he suffered ankle ligament damage in their opening 2-0 win against Serbia.
Neymar might be sidelined for Brazil's final group game against Cameroon as well, according to a report from Brazil's Globo Esporte.