Peak Is Not the Destination: The Fitness and Squad Depth Puzzle After Vietnam U23's 6-Match Unbeaten Run

When the clock ticked past the 90+3 minute at Viet Tri Stadium, a seemingly harmless ball on the right flank became the defining moment of the match. Vietnam U23 did not win, but they did not lose either. The 1-1 draw against Thailand U23 in the final group stage match is not a bad result, but for those who have followed the last 540 minutes, this is the perfect moment to ask: are we looking at a team heading in the right direction, or a team hiding fitness debts that will have to be paid in the knockout round? The context of this campaign is clear. The head coach rotated the squad in the last two group matches, making up to 7 changes from the starting lineup of the opening match. The 6-match unbeaten run is an impressive achievement, but it is built on a data foundation that I believe deserves closer scrutiny than celebratory headlines. I want to look at two specific numbers: high-intensity running distance and the number of accelerations above 25km/h in the last 3 matches. In the match against Malaysia U23, the home team only made 18 such accelerations in the second half – the lowest number of the tournament. Not because they didn't want to, but because they had no energy left. Data from the GPS sensors used by the coaching staff shows a clear trend: the group of players who started both of the first two matches saw their average distance covered drop by 9.4% in the third match compared to the first. This is not an unusual number in youth football, but it raises a big question about how we manage the squad in a tournament where matches are only 72 hours apart. Injuries don't explode in one match; they silently accumulate debt over many seasons. For U23 players, this debt is even more dangerous because their bodies are in the final stage of development, and overloading at this age can affect an entire career. What really interests me is not the 1-1 result against Thailand, but how the team handled the situation when they fell behind. Instead of increasing high-press intensity as usual, the home team deliberately lowered their defensive block, allowing Thailand to control 61% of possession, and waited for counter-attacks. This was a deliberate tactical change, but it is also a fitness signal. A high-pressing team needs to maintain a PPDA index below 8.0 for the full 90 minutes. In this match, Vietnam U23's PPDA was 11.3 – a number of a team accepting to concede the game, not a team looking for goals. I have been following this group of players since the AFC U23 Asian Cup qualifiers last September, and I notice a blind spot in how we evaluate success. We often get caught up in results but ignore the process. In the qualifiers, this team had an average expected goals (xG) of 2.1 per match. In the finals, this number dropped to 1.3. This decline does not come from the quality of chances, but from the quantity of chances created. The wide attacking plays – the team's main weapon – are becoming more predictable because the wingers no longer have the fitness to execute repeated sprints. For me, the squad depth puzzle is not about how many quality substitutes we have, but about how we use them. Rotating 7 positions in the final group match was a correct decision, but it also revealed a reality: the starting players against Thailand do not have the same level of game tempo control. They played with passion, but lacked finesse in final-third decisions. This is not a criticism, but an observation based on data: the final-third passing accuracy of the B-team was 68%, 9% lower than the A-team. If I were in the coaching staff meeting before the quarter-final, I would propose a change in approach: instead of trying to maintain pressing intensity like the first 90 minutes, accept the reality that this team may not have enough fitness to play that style for 120 minutes if extra time is needed. I would propose a more flexible model: wave pressing, where the team deliberately chooses moments to increase pressure rather than maintaining constant pressure. This model has proven effective in European youth tournaments, where match density is much higher than in Southeast Asia. Another point I want to emphasize: young Vietnamese players are facing an unprecedented congested schedule. Since the beginning of 2026, the core U23 players have played up to 34 matches including club and national team level. This number far exceeds the recommended 25-28 matches per year for players aged 20-22 according to FIFA's research on match load. It is no surprise that we are seeing a decline in fitness at the end of the tournament. The problem is not the head coach, but the system – we are asking young players to compete too much without a mechanism to protect them from their own success. The Russia World Cup taught me: reality always has the right to rebut. In 2026, I believed high pressing was the key to victory, until France only controlled 38% of possession and still beat Belgium 1-0 in the semi-final. That lesson made me always question what I see on the pitch. With Vietnam U23, I am not saying high pressing is wrong, but I am questioning its sustainability in a prolonged tournament. The map is not the territory; data is not the match. The numbers I present are only part of the picture, but they are telling a story that the 6-match unbeaten run is trying to hide. The quarter-final will be the real test. Our opponent, whoever it is, will have at least 72 hours of recovery, and they will study our three group matches carefully. They will see the fitness decline in the second half, they will see the rising PPDA numbers, and they will exploit that. The question is not whether Vietnam U23 has enough talent to win the championship – talent is always there. The real question is: are we smart enough to manage this fragile fitness resource in the most decisive moments of the tournament? Answer that question, and we will know where this team truly stands on the journey to the title.