Team Europe player Viktor Hovland will possibly be sidelined for the rest of the 2025 Ryder Cup with a neck injury during the Saturday foursomes. This situation could implement the envelope rule of the tournament, which was established in 1979. The Norwegian golfer teamed up with Robert MacIntyre to win the foursomes match on day two, but had to withdraw from the Four-ball match later in the day.The 'envelope rule' was set in 1979 when the first edition of the Ryder Cup took place between Team USA and Europe, as opposed to Great Britain and Ireland. The rule was established following the introduction of the 12 Sunday Singles matches.The envelope rule states that both captains must have selected one player from their team ahead of the tee-off; these names would be sealed in an envelope and disclosed only in the event of an injury. The captain's choice of player would withdraw from the Sunday Singles if the opponent is unable to compete. The said match point would be halved between the teams.The rule was first implemented in 1991, when American golfer Steve Pate was involved in a car accident ahead of the team event. Hence, David Gilford, whom the Team Europe captain Bernhard Gallacher named in the envelope, had to sit out the Sunday Singles. The second and only other time the obscure rule was implemented was in the 1993 Ryder Cup, when the European team's Sam Torrance sustained a foot injury. On this occasion, however, Lanny Wadkins made it easier on the U.S. captain by volunteering his name for the envelope.With Viktor Hovland now facing a neck injury, the envelope rule could be implemented for the first time in over three decades. Hovland has been struggling with his neck for over two months now and even had to withdraw from the Travelers Championship in June. However, he hopes to get treatment and compete in the singles match..Who would be Keegan Bradley's choice as per the Ryder Cup Envelope rule?Keegan Bradley with Kevin Kisner, Gary Woodland and Scottie Scheffler - Ryder Cup 2025 - Source: GettyThe U.S. captain, Keegan Bradley, will have to reveal his choice if Viktor Hovland fails to recuperate before the commencement of the Sunday Singles. Bradley will have essentially picked a player from his team who he thinks has the least chance of winning their singles match. The choice certainly won't be easy, as the 2002 U.S. captain described it as 'the most uncomfortable thing' he ever had to do.The 2025 U.S. Ryder Cup team consists of Scottie Scheffler, J.J. Spaun, Xander Schauffele, Bryson DeChambeau, Harrish English, Russell Henley, Collin Morikawa, Justin Thomas, Ben Griffin, Sam Burns, Patrick Cantlay, and Cameron Young. Bradley will have considered each player's individual performance to make the choice. The choice will only be disclosed right before the tee-off on Sunday if Hovland officially withdraws. Team USA trails behind Europe by seven points at the end of day two of the tournament.