Shin said a high level of concentration is needed for his players when they take on the two-time tournament champions.

"One percent of carelessness is not allowed for us," Shin told reporters before their training at Cheonan Football Centre. "But we've analyzed our opponents a lot, and I believe we can play a good match."

South Korea have yet to beat Portugal at the U-20 level, marking only three draws and four losses. In their latest meeting in January, South Korea and Portugal played to a 1-1 draw.

"Portugal is a strong football nation," he said. "If you look at their squad, many players are with pro clubs and they are certainly not an easy team."

Shin said he has been analyzing videos of Portugal matches and reviewed their own matches to find areas for improvement.

"We've analyzed each player's style of play and what they're good at," he said. "I've been studying what we should do to beat Portugal."

Shin hinted that there will be a slight change to the team's usual tactics. The 46-year-old tactician used a back three system against Argentina and England, and deployed a back four against Guinea in their group stage matches.

"If Portugal strikers find their scoring touch, they will be really powerful," he said. "However, I believe our players can also dismantle Portugal's defense."

Shin's side could face a penalty shootout in the knockout stage, but the head coach said he is ready.

"We should end the match in 90 matches, but we're preparing for every detail of the penalty shootout since we heard there are some changes," he said. "Our goalkeeper Song Bum-keun has been great. I have deep trust in him." (Yonhap)