Joe Nichols has canceled a Saturday night concert in Waco, Texas, and entered a substance abuse rehabilitation program. According to a message his management company posted on his Web site late Friday afternoon, "As Joe has alluded to in interviews over the past year, he has struggled with the issue of substance abuse. In order to become a healthier person and deal with longstanding issues, he has entered into a rehabilitation program for consultation and treatment." Nichols' Nashville-based publicist, Jennifer Bohler, would not comment on the situation, saying, "All I can do is point people to his Web site." The Waco Tribune-Herald newspaper reported that officials of the Heart O' Texas Fair were notified Thursday that Nichols had been hospitalized and would not be able to perform. Nichols married Heather Singleton on Sept. 9 in Savannah, Ga.