The move corresponds with the recall of left-handed pitcher Will Smith, who got the start against Seattle in the finale.
Mazzaro's latest stint with the Royals lasted just two days. He was recalled to provide long relief in Tuesday's game, throwing 2 1/3 innings and allowing three runs. He did not pitch in Wednesday's game.
On the season, Mazzaro is 3-3 in nine games (six starts) with the Royals. He's struck out 22 batters in 32 1/3 innings and has an ERA of 6.12.