African Player of the Year Sadio Mane was ruled out of the World Cup through injury on Thursday while Iran's captain urged his team to focus on football rather than anti-government protests that have rocked his country.
Mane's omission is a cruel blow for Senegal, who had high hopes of making a long run in the tournament in Qatar thanks to their star forward.
Mane suffered a shin injury playing for Bayern Munich earlier this month but was named in the World Cup squad in the hope he could regain fitness, but on Thursday Senegal conceded that the former Liverpool player would not make it.
"Unfortunately, today's MRI shows us that the improvement is not as favourable as we imagined and unfortunately we have to withdraw Sadio from the World Cup," team doctor Manuel Afonso said in a video on the official Senegal team Twitter account.
With Sunday's kick-off looming, teams are still arriving in Qatar after completing last-minute preparations.
Germany touched down in Doha on Thursday, fresh from a 1-0 friendly victory over Oman.
The 2014 champions are aiming to erase the memory of their ill-fated campaign in Russia four years ago, when they crashed out in the group stage.
Unlike most of the 32 teams who have opted to be based in and around Doha, Germany are staying in the seaside town of Al-Ruwais, 68 miles (111 kilometres) from the capital.
"We want to develop a team spirit there that will carry us through the tournament -- and for as long as possible," team official Oliver Bierhoff said.
Spain were due in Qatar in the early hours of Friday after beating Jordan 3-1 on Thursday in a friendly in Amman.
- 'Iran's minds on football' -
Iran's team are preparing with their homeland rocked by anti-government protests that have cost the lives of dozens of people and become the regime's biggest challenge from the street in decades.
Iran captain Alireza Jahanbakhsh, asked by a British journalist if his team was able to concentrate on their first match against England on Monday, said: "We are here to play football and that’s the main thing everybody is focused on while we’re here.
"We are just four days away from playing the biggest games of our lives."
On whether the players would join other Iranian sports figures who have refused to celebrate victories as a form of support for the protests, he said: "You talk about celebration; celebration is something very personal.
"Every single player has a different celebration and you ask about national anthem and that’s something that also has to be decided in the team which we already talked about."
- Heat is on -
Other teams meanwhile were adjusting to the searing heat in Doha, where temperatures nudged 34 degrees Celsius (93 degrees Fahrenheit) on Thursday.
England defender Conor Coady said his team planned to adapt to the sweltering conditions after a gruelling morning workout.
"It was hard this morning," Coady said. "Going out there and over-thinking the heat or thinking it's too hot will get us nowhere so we're going out there to embrace it."
The buildup to this World Cup has been dogged by controversy, including over Qatar's alleged human rights abuses, suppression of dissent, mistreatment of foreign workers and persecution of LGBTQ people.
Pleas from football's world governing body FIFA for a switch of focus to football have gone unheeded by some countries.
French President Emmanuel Macron insisted it was a bad idea to politicise sport and said critics of Qatar as hosts should have spoken up when they were awarded the tournament in 2010.
"I think we must not politicise sport," Macron told reporters in Bangkok, where he is attending a summit of the Asia-Pacific Economic Cooperation forum.
"These questions must be addressed when hosting the event is decided."