Commissioner Bud Selig maintains that Major League Baseball had no idea Alex Rodriguez received a medical exemption from the sport's drug administrator to use a testosterone-boosting substance in 2007.

Rodriguez received a therapeutic use exemption for the otherwise-banned substance clomid, according to the book "Blood Sport: Alex Rodriguez, Biogenesis and the Quest to End Baseball's Steroid Era," which was published last week.

Clomid is prescribed for ovulation induction and has been used by men to restore the production of testosterone following a steroids cycle. The book said the exemption was granted by Bryan W. Smith, then the independent administrator of baseball's drug program.

"We did not know about it at the time," Selig said Tuesday before the All-Star Game during the commissioner's annual meeting with the Baseball Writers' Association of America.