NEW YORK (Reuters) - The Kansas City Royals' youth movement gained more speed with 22-year-old left-hander Danny Duffy poised to start Wednesday's game against the Texas Rangers, the American League Central club said on Tuesday.
Duffy will become the ninth rookie to be used on the Royals' 25-man squad this season, according to Major League Baseball's website.
Mazzaro was optioned to Triple-A Omaha immediately after giving up 14 runs in the game, and rookie left-hander Everett Teaford swapped places with him.
Duffy registered a 3-1 record and a 3.00 earned run average in seven starts for Omaha, striking out 43 and giving up just 10 walks and 30 hits in 36 innings.
Other rookies on the roster for Kansas City (20-20) are relief pitchers Nate Adcock, Louis Coleman, Tim Collins, Aaron Crow and Jeremy Jeffress, first baseman Eric Hosmer and outfielder Jarrod Dyson.
(Writing by Larry Fine, Editing by Frank Pingue; To query or comment on this story email firstname.lastname@example.org)