RIO DE JANEIRO (AP) -- Substitutes have made a big impact at the World Cup, and there could more of them in four years' time.
FIFA's coaching advisers will propose that teams can use a fourth substitute in extra time before the 2018 World Cup kicks off.
''I think that's an idea that we will put'' to football's rules-making panel, Gerard Houllier, a member of the FIFA technical study group, said at a briefing on Tuesday.
Up to three replacements are currently allowed, even when knockout matches go to 30 extra minutes after scores are level in regulation time.
Houllier said changing the rules could see fewer players struggle with muscle cramps in high-intensity matches.
''It's a good idea. Only in extra time. Maybe if someone is injured, why not?'' the former France coach said.
So far, substitutes have scored 29 goals after coming off the bench in Brazil, already a World Cup record with eight matches left to play. The previous mark was 23 at the 2006 tournament in Germany, FIFA said.
''Substitutes play such an important part because they come with a freshness and attitude,'' Houllier said. ''Nearly a quarter of (all) the goals have been scored in the final 15 minutes of the game.''
Those goals by subs have often been game-changing, rather than additional scores in blowout victories.
Klaas-Jan Huntelaar came on late when the Netherlands were losing 1-0 to Mexico in the round of 16 on Sunday. Huntelaar teed up Wesley Sneijders for an 88th-minute leveler then scored the decisive stoppage-time penalty.
On Monday, Belgium could not beat inspired United States goalkeeper Tim Howard until substitute Romelu Lukaku was sent on in extra time, and quickly set up Kevin De Bruyne for the go-ahead goal, then scored the second in a 2-1 win. The USA's goal was scored by substitute Julian Green, moments after he entered the game in extra time.
The Americans also got a decisive late goal in its opening group match from defensive replacement John Brooks.
FIFA has asked Houllier's group to propose ideas football's rules panel, which is known as IFAB.
The panel has previously rejected the fourth sub plan, though Houllier suggested it could be revisited.
''At this World Cup everything is going so quick, so fast, the tempo has been so high,'' he said. ''As a technician we would like to have in extra time the possibility to have another substitution.''