Coach Kim Sang-sik and the squad optimization puzzle: From AFF Cup 2026 to Asian Cup 2027

Coach Kim Sang-sik and the squad optimization puzzle: From AFF Cup 2026 to Asian Cup 2027

Hook

On the evening of January 5, 2026, at Rajamangala Stadium, the final whistle of the AFF Cup 2026 second-leg final echoed. The score was 3-3 after 120 minutes, and Thailand climbed to the champion's podium via the away goals rule. But for those who followed Vietnam's entire journey under Coach Kim Sang-sik, the most telling number was not the scoreline — it was that 7 players under 23 years old logged a combined 1,240 minutes throughout the tournament. Numbers do not lie; they only wait for us to read them correctly.

Context

When Coach Kim Sang-sik took over the Vietnam national team in May 2026, fans posed two major questions. First, could the Korean strategist maintain the possession-based identity that predecessor Park Hang-seo had built over five years? Second, how deep would the squad rotation go, given that the U23 generation who won the 2026 SEA Games gold were now 23-24 years old and needed first-team opportunities?

AFF Cup 2026 was the first test. The tournament ran from December 2026 to January 2026, featuring 7 matches in 4 weeks — a grueling schedule demanding squad depth. Vietnam was placed in Group B alongside Indonesia, Philippines, Myanmar and Laos, then overcame Singapore in the semifinals before facing Thailand in the final.

Core

Three days of rewatching the tape, then one detail reveals itself.

The first thing to note: Kim Sang-sik did not copy Park Hang-seo's formula. Under Park, Vietnam operated in a 3-4-3 or 5-3-2 system, prioritizing defensive numbers and counter-attacks. Kim brought a different philosophy: high pressing and rapid ball circulation through midfield.

Data from all 7 matches at AFF Cup 2026 shows:

• Average possession: 58.3% — 7.2% higher than AFF Cup 2026 under Park (51.1%).
• Passes per match: 487 — compared to 412 in 2026.
• Pass accuracy: 83.7% — up 4.1%.
• Average shots per match: 14.2 — 3.8 more than the previous tournament.

But the most impressive number lies in pressing frequency in the opponent's final third: 12.3 times per match, double the 6.1 figure from 2026. This is Kim Sang-sik's clearest tactical imprint: he wants the team to win the ball back high up the pitch, rather than dropping deep to wait.

However, high pressing demands fitness and synchronization. In the second-leg final against Thailand, after the 70th minute, Vietnam's players began to fade. The pressing lines broke, gaps appeared between midfield and defense. Thailand exploited this weakness precisely, scoring 2 goals in the final 15 minutes.

Frequency is what fans overlook, but coaches do not.

Another critical detail: how Kim Sang-sik deployed his personnel. Among the 26 players called up, 9 came from the U23 cohort (born 2026-2026). Midfielder Nguyen Thai Son (21 years old) played 5 matches totaling 387 minutes — the most among young players. Defender Phan Tuan Tai (22) started 4 matches on the left flank.

This suggests Kim Sang-sik is executing a deliberate generational transition plan. He has not discarded veterans entirely — Que Ngoc Hai (31) remains the defensive leader with 6 starts — but gradually integrates younger players into the system.

Contrarian

When the stands are empty, the pitch begins to tell the real story.

A common narrative holds that AFF Cup 2026 was a failure because Vietnam did not win. But based on my experience tracking matches across multiple tournaments, I see this as a controlled step forward — and more importantly, it exposed structural issues that Park Hang-seo's success had masked.

First, the fitness problem in the final 20 minutes.

Under Park, Vietnam typically dropped deep and preserved leads. Kim demands 90-minute pressing, but the players' fitness has not caught up. In 4 official matches (semifinals and final), Vietnam conceded 5 goals from the 70th minute onward — 62.5% of total goals against. This is a clear warning signal.

Five substitutions help deep squads, but also turn the final 20 minutes into an attrition war. Kim used an average of 4.1 substitutions per match — below the maximum. He appears not yet fully confident in his bench options, particularly at the center-forward position.

Second, the naturalized striker puzzle.

The call-up of Nguyen Xuan Son (Rafaelson) — a Brazilian-born naturalized striker — was a controversial decision. He scored 3 goals in 5 matches, but his integration into Kim's pressing system has been uneven. In pressing situations, Xuan Son often lagged 1-2 steps behind his teammates, creating gaps between the lines.

Third, the absence of a top-class central midfielder.

Since Nguyen Quang Hai's form dipped after returning from France, and Nguyen Hoang Duc has not rediscovered his best version, Vietnam's midfield lacks a true orchestrator. While Thai Son and Van Khang have performed well, they still lack big-match experience. This is the position most in need of upgrade.

Takeaway

Before believing a rumor, I count every play.

AFF Cup 2026 was not a failure. It was a deliberate test — Kim Sang-sik used the tournament to trial a new system, integrate the next generation, and expose weaknesses that need fixing. The question is: will the coaching staff have enough time and resources to patch these holes before Asian Cup 2027?

I choose to trust the tape, because the tape has no emotions.

Looking ahead, I will track three signals in 2026: (1) the team's pressing frequency in friendlies against stronger opponents, (2) the playing minutes of U23 players in V-League, and (3) how Kim adjusts tactics against European and African teams — where fitness and speed are decisive factors.

Football is not in a hurry; neither is the writer. The road to Asian Cup 2027 is long, and the lessons from AFF Cup 2026 will serve as the foundation — if we know how to read the numbers correctly.