Spain included Barcelona's Ansu Fati but left out Liverpool midfielder Thiago Alcantara and Manchester United goalkeeper David de Gea from their 26-man World Cup squad on Friday.
Fati, now 20, made his international debut in 2020 at 17 and in his second game became the youngest player to score for Spain, breaking a record held since 1925 by Juan Errazquien.
But the forward is fighting his way back from four surgeries to repair an injury to his left knee, suffered in November 2020.
De Gea has fallen out of favour with Luis Enrique who said in March he "wanted to test other goalkeepers" and Thiago saw his role diminish with the rise of Barca teenagers Pedri, 19, and 18-year-old Gavi.
"Youth gives you freedom because you are not yet aware of the consequences," Luis Enrique said. "Yet, most of the youngsters that are with us are already in high-level teams.
"The bar that I'm setting is infinity. My goal is to compete in every game.
"There's no one outside of Spain who rules out Spain as a candidate to be among the best. We are going to give war, there is no doubt."
Spain have been drawn in Group E with Costa Rica, Germany and Japan.
Serbia's all-time top scorer Aleksandar Mitrovic, who is nursing an ankle injury, was named by coach Dragan Stojkovic in their 26-man squad for the World Cup in Qatar.
Fulham striker Mitrovic, who missed their Premier League defeat to Manchester City last weekend and is a doubt for Sunday's game against Manchester United, has bagged 50 goals for his country and is in the squad along with Juventus striker Dusan Vlahovic.
The duo, who have scored 17 goals between them for their clubs this season, are expected to lead the line for Serbia at the tournament with Fiorentina's 24-year-old Luka Jovic waiting in the wings.
Serbia will be captained by Ajax Amsterdam's Dusan Tadic, who has 90 caps for the national team, scoring 18 times.
Their midfield will also be led by Lazio's versatile Sergej Milinkovic-Savic, who has six goals in 35 appearances for the national team.
Serbia are in Group G alongside Brazil, Switzerland and Cameroon. Serbia, who have never moved past the group stages, take on five-times champions Brazil in their opening group game on 24 November.
Sadio Mane has been named in Senegal's squad for the World Cup in Qatar despite injury concerns after he was hurt playing for his German club at the weekend.
Mane was forced off after 20 minutes and the Senegal international will undergo an X-ray to determine the extent of the problem.
Senegal begin their World Cup campaign against the Netherlands on 21 November and also face hosts Qatar and Ecuador in Group A.
Bayern coach Julian Nagelsmann told a post-match press conference: "He took a blow to his tibial plateau. It's a painful spot. He’ll have to have an X-ray to see what’s happened."
But Senegal coach Aliou Cisse included the team’s talisman when he named his 26-man squad at a news conference in Dakar on Friday.
The former Liverpool striker is Senegal's record goalscorer and scored the decisive penalty as his country beat Egypt to win the Africa Cup of Nations earlier this year.
Netherlands have included injured Barcelona forward Memphis Depay and uncapped teenager Xavi Simons in their 26-man World Cup squad but left out veteran goalkeeper Jasper Cillessen.
Depay has not played since limping off during the Nations League match against Poland on 22 September, and has played less than 150 minutes for Barcelona this season.
"He is fit to play from a medical perspective, but we will have to build Depay up," coach Louis van Gaal told a news conference.
The injury of Depay, who was involved in 18 of the 33 goals the Netherlands scored in the qualifying campaign, is a serious risk for the side's chances, Van Gaal said, but does not change their ultimate objective.
"We have one goal, to become world champions. With our team spirit we definitely have a good chance," said the 71-year old former coach of Ajax Amsterdam, Bayern Munich and Manchester United.
Simons, 19, has made a strong impression since his move from Paris St Germain to PSV Eindhoven in the close season, scoring eight goals in 13 league matches.
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