Japan defeated Iceland 1-0 in an international friendly on Tuesday in a match that highlighted the impact of a newly introduced FIFA substitution regulation ahead of the next World Cup.

The decisive moment came late in the game when Iceland was temporarily reduced to 10 players after failing to comply with a new International Football Association Board rule aimed at speeding up substitutions and reducing time-wasting.

Under the updated regulation, any player being substituted must leave the pitch within 10 seconds and exit through the nearest boundary line. Failure to do so means the incoming substitute cannot enter immediately, forcing the team to continue with 10 players until the next stoppage and at least one minute has elapsed.

Iceland encountered problems during a late substitution involving winger Isak Thorvaldsson after the outgoing player delayed leaving the field.

Japan capitalised on the numerical advantage almost immediately.

Striker Koki Ogawa scored the winning goal in the 87th minute with a header, less than two minutes after Iceland were left temporarily short-handed.

The goal came exactly 1 minute and 54 seconds after the substitution, showing how quickly the new law can affect the outcome of matches.

After the game, Japan coach Hajime Moriyasu said his players adapted well to the new rules but warned that teams must remain alert.

“The players handled the new rule adjustments today with almost no issues,” Moriyasu said.

“But under the new rules, substitutions won’t always be as straightforward as before. We need to stay alert so we don’t create openings for the opponent.”

Moriyasu also pointed to other upcoming rule changes, including three-minute hydration breaks that will allow coaches to brief tactical discussions during games.

The friendly served as an early test of several new football regulations being introduced ahead of the World Cup, including stricter time limits for throw-ins and goal kicks, mandatory off-field treatment periods for injured players, and expanded VAR reviews.

For Iceland, a delayed substitution proved costly. For Japan, the victory demonstrated how even small details under the new rules can decide matches.