Kansas City Royals outfielder Kyle Isbel (hamstring) will head to Triple-A Omaha on Tuesday to begin a rehab assignment. Isbel injured his left hamstring back on May 4 while running out a bunt for a base hit. Kansas City plans to have him spend a couple of weeks with Omaha until he's 100%. Isbel will take over as the Royals' starting center fielder when he's ready to return from injury.