Moustakas, who on Friday was announced as the winner of the fan vote for the final spot on the American League All-Star team, missed four games.
The issue that led to his absence was undisclosed. Moustakas is hitting .301 in 75 games this season.
To make room on the roster, infielder Cheslor Cuthbert, who had a hit in all four games he played with the Royals, has been optioned to triple-A Omaha. The Royals went 4-0 with Cuthbert starting at third base.
Relief pitcher Neftali Feliz told the Texas Rangers he would not accept an outright assignment to the minor leagues, exercising his right as a five-year veteran and making him a free agent. The 2010 AL rookie of the year and former All-Star closer was designated for assignment July 3. . . .
Washington placed center fielder Denard Span on the 15-day disabled list because of back spasms. . . . Boston right-hander Clay Buchholz left his start against the Yankees in the third inning because of tightness in his throwing elbow. . . .
The Chicago Cubs said they do not expect starter Jason Hammel to miss a turn in the rotation because of the hamstring tightness that caused him to leave Wednesday's game against St. Louis.