The National Women’s Soccer League will implement a series of rule changes beginning with this weekend’s Challenge Cup between NWSL champions Gotham FC and Shield winners Kansas City Current. Some of the measures, focusing on player safety and fan behavior, were adopted for the first time at the 2026 FIFA men’s World Cup.One of the changes — developed in consultation with the NWSL Players Association, clubs, medical and competition staff and the Professional Referee Organization (PRO) — will see a new off-field treatment rule and a timed substitution rule. Additionally, the NWSL will update its game day heat safety policy and expand its fan code of conduct to cover digital and social media spaces.Under the new off-field treatment rule — the most significant on-field change, mirroring a rule introduced at this summer’s World Cup — players who remain on the ground and require medical personnel to enter the field after play is stopped will be required to leave the field for a one-minute treatment period. This rule was previously used in Major League Soccer. The clock begins once play restarts, with the fourth official monitoring the countdown before the player is permitted to return.The league said the measure is designed to reduce unnecessary stoppages and improve match flow.The NWSL will also implement a timed substitution rule aimed at discouraging time-wasting. Players being substituted will now have 10 seconds to leave the field. Failure to do so will result in the incoming substitute being delayed from entering until the next stoppage after a one-minute waiting period. This would force the offending team to temporarily play down a player.