South Korea have already qualified for the men's football tournament at the Rio de Janeiro Summer Games after finishing second at the Asian Football Confederation (AFC) U-23 Championship in January, but that doesn't mean players can afford to relax.

For footballers aged under 23, the competition for roster spots is just heating up, with no one having been guaranteed a spot on the final 18-man roster. For them, the two friendly matches against Algeria this month is a great opportunity to impress head coach Shin Tae-yong and put their names on the team.

South Korea face Algeria, which also qualified for the Rio Games, on Friday at Icheon Sports Complex in Icheon and next Monday at Goyang Stadium in Goyang, both in Gyeonggi Province.

Shin said that against Algeria, he will carefully watch those who haven't played regularly with the Olympic football team and players who are playing on foreign clubs.

"I told our players where this team is going and what we should do," Shin said Monday before practice at the National Football Center (NFC) in Paju, north of Seoul. "I asked them to forget the past and work hard for a fresh start."

In the Summer Games, 16 countries will each send a team of 18 footballers. The quadrennial event is open to players under the age of 23 at the start of the Olympic year, but teams can also field up to three players who are over the age limit, known as wild cards.

The addition of these wild cards, who usually come from the senior national team, will heat up the competition for the final roster, putting that much more burden on young players.

Considering that three slots are reserved for wild cards and two spots are given to goalkeepers on the 18-man roster, this means only 13 field players under 23 can go to Brazil. At the previous Olympics in 2012, South Korea used one of the three wild cards on veteran goalkeeper Jung Sung-ryong, but Shin has already said he will use all of his three cards on field players.

South Korea have called up 21 field players for friendlies against Algeria. Not included this time is Red Bull Salzburg forward Hwang Hee-chan, who played an integral role on offense to help South Korea clinch the Olympic berth. Shin said he'd rather save him now and call him up just before the Olympics, making the 20-year-old as close to a sure bet as there is for the final team.

The rest of the team knows the situation is only getting more intense.

"Because only a small number of players can be listed on the final roster, we're feeling the pressure of the competition," said Pohang Steelers midfielder Moon Chang-jin on Tuesday. "We don't even talk to each other as often as we did in the past."

While young players are feeling the pressure, Shin has already told them what to do if they want to earn a selection. He said those who are regular starters at their clubs will have an advantage.

"They can keep the rhythm of the game by playing regularly at their clubs," he said. "By doing so, they will also be able to survive on the national team."

There will be a competition in the wild-card selection, too.

Shin said one of the three wild cards will be Son Heung-min, revealing that the Korea Football Association (KFA) already asked his English club Tottenham Hotspur for cooperation to release the forward before the Rio Games. Because the multisports event is not organized by FIFA, professional clubs are not mandated to release players over 23 for the Olympics.

The 45-year-old coach, also an assistant to the men's senior football team head coach Uli Stielike, said he will announce other two wild cards after watching the Olympic group draw next month.

But players like FC Porto striker Suk Hyun-jun have already expressed their desire to play for the Olympic team. Suk said he would even persuade his Portuguese club if it doesn't release him.

For South Korean male athletes, winning an Olympic medal not only brings national honor but also an exemption from the mandatory military service. Footballers who haven't completed their military service have been considered top wild card candidates, because they will have extra motivation at the tournament.

However, Shin said that he won't prioritize players who haven't completed their military duty when it comes to wild-card selection.

"I can still choose players that have already completed their military service, if they can contribute to our team," he said. "I think it's okay for them to join us and help the rest of the team get the same benefits."

Shin said it is now up to players to determine their fate as the competition on the squad has become obvious. He emphasized that even if they fail to show a good performance in friendly matches against Algeria, there will be another chance. South Korea are planning to have up to two friendly matches between May 30 and June 7, though opponents and venues have yet to be decided.

"I want to see our players compete against each other and raise their levels higher," he said. "I expect to see players work harder even if they go back to their clubs and then make themselves better when they can come back to the Olympic team next time." (Yonhap)