Vietnam U23 meets South Korea U23 in the Asiad 2026 quarterfinal: Why the defending champions must remind each other not to be complacent

At 17:30 on September 25, in Japan, Vietnam U23 steps into the men's football quarterfinal of Asiad 2026 against defending champions South Korea U23. After the 2-0 win over Saudi Arabia U23, South Korea captain Lee Gi Hyuk said a sentence I copied verbatim into my notebook: "Vietnam U23 has just suffered a defeat to Uzbekistan U23. So they will enter the quarterfinal with very high determination. Therefore, I reminded my teammates that we must not be complacent and must always maintain a high level of focus." The man who said it is a centre-back who can also play defensive midfield for Gangwon FC, one of South Korea's three overage players. He had just suffered a bruised shin after a collision in the 27th minute against Saudi Arabia, still finished the match, and according to The Chosun, is fully available to face Vietnam U23. What stands out is that Lee Gi Hyuk did not spend a single sentence on his own injury. He talked about the opponent. From the wet grass of Trigoria, I learned to hear the future before others could see it. That afternoon, in the captain's voice, what I heard was not the arrogance of a strong team, but the wariness of a side that had once been beaten by this very opponent. The context deserves recalling. At the AFC U23 Asian Cup 2026 held in Saudi Arabia last January, South Korea U23 lost to Vietnam U23 6-7 on penalties, after the two sides drew 2-2 over 120 minutes in the third-place match. For Vietnamese youth football, that was one of the rare nights the team stood firm against a top continental football nation for two full hours. Eight months later, the picture has changed. At Asiad 2026, Vietnam U23 is weakened by the absence of Dinh Bac and a few key defensive players. South Korea U23 has grown noticeably stronger, adding 9 players currently playing in Europe and 3 overage players. With that squad, they beat Qatar U23 4-1 and Saudi Arabia U23 2-0, topping Group D. On the coaching bench, Vietnam U23 does not have coach Kim Sang Sik. Sports Hankook noted this detail as a point of concern, while issuing a warning: "South Korea U23 absolutely must not be complacent." The Korean outlet judged that Vietnam U23 still possesses traits that can trouble their opponent, especially the ability to organise defence and switch quickly into attack. From the perspective of someone who follows teams for a living, this contrast is more interesting than any scoreline. One side has lost players, and even the man directing from the bench. The other has added nine players from Europe and three overage players. And yet it is the higher-rated side that must remind itself not to be lax. I followed Vietnam U23's matches at Asiad 2026 and recorded the repeating patterns. Sports Hankook describes accurately what I saw: pragmatic defending, fierce pressing in midfield, and quick counterattacks into the spaces on both flanks. The Korean outlet calls that Vietnam U23's weapon. There is one line in the Sports Hankook piece I want to dwell on longer. The outlet wrote that Vietnam U23's most frightening quality lies in their durable physical base and their nothing-to-lose mentality, rather than in the names of their players. This is a notable assessment coming from the opponent, because it admits that what Vietnam U23 owns does not belong to any single individual. Let us analyse with numbers. A team that organises defence in a block and presses in midfield tends to burn stamina very quickly in the final 20 minutes. But a team that switches quickly into attack has the opposite advantage: they do not need much possession, they need moments of explosion. The five-substitution rule deepens squads, but it also turns the last 20 minutes into a war of attrition. For a counterattacking side, this is a double-edged sword. If the coach uses all his substitutions to protect a scoreline, he hands the match to the opponent himself. If he keeps one back to reinforce the attack, he can produce a surprise. For South Korea U23, five substitutions are a tool for rotating a deep squad. Nine players from Europe plus three overage players mean they can change an entire midfield without losing quality. That is an advantage Vietnam U23 does not have. Lee Gi Hyuk's role deserves separate analysis. He plays both centre-back and defensive midfield. With a squad full of European-based attackers, his job shielding the back line is pivotal. If Vietnam U23 counter quickly down the flanks, Lee Gi Hyuk is the one who must cover for the advancing full-backs. A bruised shin might not stop him running, but it makes every turn of the body more costly. The spaces on both flanks are where the match will be decided. South Korea U23, with a strong attack, will push their shape high, dragging both full-backs forward. Behind them lies the space any counterattacking team craves. Sports Hankook rightly points to this when speaking of quick counters into the wide channels. That is not a generic remark. It is a map directing Vietnam U23. But a squad advantage only turns into goals when there is cohesion. Nine new players from Europe, three overage players, plus those who played at the U23 Asian Cup last January. That squad needs time to understand one another. In the group stage against Qatar and Saudi Arabia, South Korea U23 won on the strength of individual quality. But in the quarterfinal, when the opponent sits deep and waits for an opening, cohesion becomes far more important. A team assembled from many pieces can get through a group stage on individual strength. To win a match in which the opponent concedes possession and only waits to counter, that team needs something else: tactical patience. And patience is not something bought with the number of matches played in Europe. I have spent many mornings standing outside training-ground fences watching youth teams. I have stood outside the fence long enough to know that even stars lose their balance sometimes. What I took from it: big teams often lose not because they lack talent, but because they are dragged into the rhythm of a smaller opponent. When Vietnam U23 deliberately plays slowly, defends in a block and only bursts out a few times, they pull South Korea U23 into a match where every moment must be decided in a split second. For a newly assembled squad, those moments are where errors appear. Look back at the third-place match at the AFC U23 Asian Cup 2026 last January. Vietnam U23 drew 2-2 with South Korea U23 over 120 minutes and won on penalties. It was a match in which South Korea U23 held more of the ball but could not finish off their opponent. That scenario, if repeated in the Asiad 2026 quarterfinal, is something coach Lee Min Sung must factor in. In the online survey of 3,000 Vietnamese fans I conducted before the Asiad, one result made me think. Most respondents said their biggest concern was a defence missing players, yet their greatest belief was in the counterattack. The fans' worry and their faith, it turned out, point to two sides of the same road: the team must endure pressure, but it must also exploit space. The journey from Russia to Anfield was not a contract, but a quiet promise. I learned that while following a goalkeeper through a World Cup, and I see it repeated here. Smaller teams do not need a blockbuster signing to create a memorable night. They only need a promise to themselves, and an opponent who is complacent. The outside view, especially in international reports, tends to paint a simple picture: South Korea U23 stronger, Vietnam U23 weaker, and the quarterfinal merely waiting for a result. That reading ignores the volatility inherent in youth football. It also ignores something subtler that captain Lee Gi Hyuk himself touched on. A strong team sometimes does not fear a strong opponent. It fears an opponent with its back to the wall. A team that just lost to Uzbekistan U23 will enter the quarterfinal with a different mentality than a team that just won 2-0. In sports psychology, the nothing-left-to-lose state generates a form of energy that cannot be planned for. South Korea U23 knows this, and Lee Gi Hyuk said it out loud. There is one more point international reports often skip. Vietnam U23 does not have coach Kim Sang Sik on the bench. Many treat this as a pure disadvantage. But in football, the absence of a familiar commander sometimes forces the players to organise themselves. And a team that organises itself is often more cohesive than one waiting for orders from the bench. This is what I have observed in youth teams over many years. It is not a designed advantage, but a real psychological response. Talent does not lie in a beautiful passage of play, but in how a boy gets back up after a ruined one. Vietnam U23 enters this match after a defeat. The way they get back up will say more than any possession statistic. I am not saying Vietnam U23 will win. I am saying that calling them underdogs does not mean the match is decided. Asian youth football is full of nights when the higher-rated team leaves the pitch in silence, and the third-place match in Saudi Arabia last January is an example still fresh in both teams' memories. At 17:30 on September 25, in Japan, both teams will walk onto the grass. South Korea U23 carries nine European-based players, three overage players, and a captain with a bruised shin. Vietnam U23 carries a defence missing players, an unusual coaching bench, and a memory of a penalty night in Saudi Arabia. Who holds the upper hand is perhaps not hard to guess. But what decides the match may lie somewhere the scoreboard does not show. The question I asked myself as I closed my notebook: if South Korea U23 must remind each other not to be complacent, what exactly does Vietnam U23 hold that makes a strong team so wary? And will that be enough to create one more night when the heartbeat of Vietnam's football community beats louder than any bet?