Source: Thomas to retire

Former Chicago White Sox slugger Frank Thomas has called a news conference for 11 a.m. Friday local time at U.S. Cellular Field to announce his retirement.

The White Sox are expected to announce at that time that Thomas' No. 35 will be retired this summer, according to major league sources. A source speculated the ceremony might occur Aug. 2, the 20-year anniversary of when Thomas broke in with the Sox.

MLB.com first reported that Thomas would retire. Thomas, who played for the White Sox from 1990 to 2005, told MLB.com he spent last winter, as well as much of this offseason, thinking about his future and waiting for offers that never surfaced.

The five-time All-Star is thought to be a strong contender for the Baseball Hall of Fame when he becomes eligible in 2014.

Thomas, arguably the greatest player in White Sox history, holds numerous team records, including all-time home run and RBI marks. Thomas, who turns 42 on May 27, has pursued a career in broadcasting since failing to hook on with a team after 2008.

Bruce Levine covers baseball for ESPNChicago.com.