After securing a contract buyout from the Milwaukee Bucks on Thursday morning, Butler is expected to clear waivers and become a free agent.
San Antonio and Chicago are in pursuit and plan to make pitches for Butler too, league sources said.
The fact that Oklahoma City stopped pursuing Danny Granger has led many in the NBA to believe the Thunder are confident in their recruitment of Butler.
The Los Angeles Clippers are strong leaders to sign Granger, sources told Yahoo Sports.
The acquisition of Butler, who earned All-Star honors in the 2006-07 and 2007-08 seasons, could be a tremendous boost to the Thunder and Heat's pursuit of an NBA championship. Despite initial reports that Butler was destined to sign with Miami, Oklahoma City has a strong chance to land Butler, sources told Yahoo Sports.
The Heat are competing to lure Butler back to where his career started as the 10th overall pick in the 2002 NBA draft, but the ability to fill the gap as a complementary scorer to Thunder stars Kevin Durant and Russell Westbrook has made the Thunder an attractive destination, league sources told Yahoo Sports.
Oklahoma City could move Durant to power forward and slide Butler into the small forward spot in different lineup variations.
Butler, 33, averaged 11 points in 34 games for Milwaukee this season. Butler has averaged 15.3 points per game in his 12-year career.
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