The US Golf Association, along with Britain's Royal & Ancient Golf Club, approved a rule that prohibits the use of a putting stroke that uses the body as a anchor.
Tiger Woods and Rory McIlroy were both beaten in first round matches at the Accenture Match Play Championships Thursday in Arizona.
The Royal & Ancient Golf Club and the U.S. Golf Association said the proposed rule would make it illegal for pro golfers to "anchor" the club to their bodies while making a stroke. The new rule would not take effect until 2016.
The former PGA champion went low again for a second day at the third event in the FedEx playoff chase in Indiana.
Scoring conditions were good early in the first round of the PGA Tour's final major of the year, being played at Kiawah Island, South Carolina.