Davis worked in the energy industry for forty years, until he retired as the CEO of ETP and ETE in 2007. He remained with the company as a director, and operates Avatar Investments LP, a Dallas-based investment firm. In 2008, Davis made his first appearance on the Forbes 400 list, ranking 367th with a net worth of $1 billion. In 2012, he ranked 315th with a net worth of $1.5 billion, and he ranked 296th in 2013 with a net worth of $1.9 billion.
When the Rangers were put up for sale in 2010, Davis joined a group headed by Chuck Greenberg and Nolan Ryan, which purchased the club. Davis and Bob R. Simpson provided the majority of the $593 million sale price. Davis and Simpson became co-chairmen of the Rangers, but remained mostly behind the scenes as senior consultants while allowing Greenberg and Ryan to operate the team as CEO and president, respectively. This arrangement continued after Greenberg left in 2011 and ceded his post as CEO to Ryan. Following Ryan's resignation from the Rangers in 2013, Davis was approved by MLB as the team's control person, thus making him the primary person accountable to the commissioner's office for the team's operations.