Can Lee Min-sung's side find the form to challenge Japan?

South Korea's under-23 men's football team, led by head coach Lee Min-sung, faces Vietnam in the quarterfinals of the 2026 Aichi-Nagoya Asian Games on Friday at 7:30 p.m. at Mizuho Park Rugby Stadium in Nagoya, Japan. Korea advanced to the last eight as Group D winners after defeating Qatar 4-1 and Saudi Arabia 2-0.

The results are perfect on paper, but questions linger about the team's performances. As Lee's side chases a fourth consecutive Asian Games gold medal, concerns over its level of play heading into the Vietnam quarterfinal are hard to ignore.

The biggest worry stems from Tuesday's match against Saudi Arabia. The Saudis, averaging 21 years of age — two years younger than Korea — sat deep and relied on physical duels and intense pressing. Korea made frequent passing errors in buildup play and struggled to generate clean attacking moves. The team's first shot did not come until the 22nd minute, off the boot of Yang Min-hyeok. In the 34th minute, Korea came close to conceding from a Saudi corner kick. Early in the second half, goalkeeper Kim Jun-hong had to make a key save to deny a Saudi breakaway.

The momentum shifted after Bae Jun-ho came on in the 50th minute. In the 67th minute, Eom Ji-seong delivered a free-kick cross that Shin Min-ha headed home, and two minutes later Kim Myeong-jun converted another header from a Bae Hyeon-seo cross. Both goals came from crosses — it was set pieces and individual deliveries, not organized attacking play, that finally broke down Saudi Arabia's compact defense.

KBS commentator Lee Young-pyo, who called the match, said Korea "made many passing mistakes from early in the first half and failed to press the opponent's buildup play, allowing them to advance into our half far too easily — we made the game hard for ourselves." He added that the players' "mental preparation and physical condition did not seem to be at 100 percent," and stressed that "more preparation is needed for the quarterfinal."

Tactically, the team's attacking play has been criticized for its lack of variety. Eom Ji-seong and Bae Jun-ho have been in good form, but the offense has leaned too heavily on the two players' runs down the flanks. With the team's passing combinations and link-up play still far from polished, there is no clear alternative when the wide channels are closed off.

Set pieces remain another concern. The winning goal did come from a free kick, but Korea squandered several other scoring opportunities from dead-ball situations — particularly at corner kicks, where rehearsed movements and pre-planned patterns were rarely visible. Lee Young-pyo said it "also bothers me that Korea failed to threaten the opponent despite having quite a few set-piece opportunities," though he added that the team "may have been concealing its set-piece tactics ahead of the knockout rounds."

Amid these concerns, Lee has made significant changes to his starting lineup for the Vietnam match. Kim Jun-hong will start in goal, with Bae Hyeon-seo, Shin Min-ha, Kim Ji-su and Choi Seok-hyeon forming the back line. Captain Lee Gi-hyeok and Kang Sang-yun will anchor the midfield, while Bae Jun-ho, Lee Hyeon-ju and Yang Min-hyeok line up behind striker Lee Yeong-jun.

Kim Myeong-jun, Lee Seung-won and Eom Ji-seong — all of whom started both group-stage matches — will begin on the bench, a rotation that reflects the squad's two-day turnaround after the Saudi Arabia game. The notable variable, however, is that Yang Min-hyeok and Lee Hyeon-ju, both criticized for looking sluggish against Saudi Arabia, are back in the starting lineup. Neither has been getting consistent playing time at their clubs, and both have been questioned on fitness. If the new combination fails to unlock the attack — with consecutive-goal scorer Kim Myeong-jun and attacking linchpin Eom Ji-seong both absent from the XI — the same frustrating display seen against Saudi Arabia could repeat itself.

Lee has made clear he will prioritize results over performance. After the Saudi Arabia match, he said, "From the quarterfinals onward it's a knockout tournament, so we have to take a more conservative approach," adding, "Fans will want both good football and results, but from here on we will play with a clear focus on getting the result."

On paper, Korea holds the stronger hand. Vietnam is without head coach Kim Sang-sik, who knows Korean football well but skipped this tournament to focus on senior-team fixtures in September and October. Assistant coach Dinh Hong Bin is in temporary charge, and key players including striker Nguyen Dinh Bac have been called up to the senior national team. Vietnam finished second in Group C with one win, one draw and one loss. Korea, by contrast, bolstered its squad with wildcard players — those selected without age restrictions — Lee Gi-hyeok, Eom Ji-seong and Yang Hyeon-jun, along with a large contingent of overseas-based players.

Still, there is no room for complacency. Korea leads the all-time record against Vietnam at the U-23 level with six wins and four draws, but one of those draws stings. In January, Korea drew 2-2 with Vietnam in the third-place match at the AFC U-23 Asian Cup and then lost 6-7 on penalties to finish fourth — officially a draw, but in effect the first time Korea had been beaten by Vietnam.

The bigger concern lies beyond the Vietnam match. A win on Friday would set up a semifinal on Wednesday against the winner of the China-Thailand match, and a potential final against Japan — the most likely rival for gold. Japan assembled its squad from U-21 players with an eye on the 2028 Los Angeles Olympics, but the team remains formidable. Lee's side lost 0-1 to Japan in the semifinals of the January AFC U-23 Asian Cup. That is why analysts say a repeat of the Saudi Arabia performance would not be enough to beat Japan. The Vietnam quarterfinal is not just about reaching the semifinals — it is a chance for Lee's side to prove that the concerns about its form are unfounded.