Aoki, who grounded out as a pinch hitter in the ninth inning Friday, is hitting .263 with 14 extra-base hits, in 68 games, while batting leadoff in 64 games.
The Royals purchased the contract of outfielder Justin Maxwell from Triple-A Omaha, where he was hitting .316 with five doubles, a triple, five home runs and 18 RBIs in 25 games.
Maxwell began the season with Kansas City, but was designated for assignment on May 15 with a .138 average. Maxwell started in right field Saturday against the Seattle Mariners.
The Royals transferred left-handed pitcher Bruce Chen, who went on the disabled list May 2 with a bulging disk, to the 60-day disabled list to make space for Maxwell on the 40-man roster.