Muhammad Ali, the former world heavyweight boxing champion, visited the clubhouse of the San Francisco Giants on Tuesday as the team continued its Major League Baseball pre-season training.

The 68-year-old superstar, who suffers from Parkinson's disease, is visiting teams that train near his Arizona home in hopes of recruiting players to donate their time as part of the Athletes for Hope program.

"It's exciting. He is one of the greatest," said southpaw pitcher Jonathan Sanchez. "To have someone like him here makes you be better every day."

Ali, whose friends include retired Giants' Hall of fame legend Willie Mays, is among the founding members of Athletes for Hope, which is dedicated to community service and includes US cycling star Lance Armstrong and tennis great Andre Agassi among its members.