To clear room on the 25-man roster for Frasor, the Royals optioned right-hander Louis Coleman to Triple-A Omaha. To open a spot on the 40-man roster, they designated infielder-outfielder Jimmy Paredes for assignment.
Frasor, 36, is 1-1 with a 3.34 ERA in 38 relief appearances this year. He has 30 strikeouts and 14 walks in 29 2/3 innings.
Frasor began his career with the Toronto Blue Jays and also pitched for the Chicago White Sox. In 624 games, he has a career record of 31-35 and an ERA of 3.65.
Coleman, one of the Royals' most reliable relievers last season, has encountered rough going this year. He won his only decision but has a 7.48 ERA in 20 games, giving up 31 hits and 13 walks in 21 2/3 innings.
Coleman started the season on the disabled list because of a jammed finger on his pitching hand, sustained early in Spring Training. This is the third time he's been sent to Omaha this season.
Coleman was last recalled a week ago for the Detroit series and got into two games. Last Thursday, he gave up five hits and four runs in 1 2/3 innings. On Saturday, he retired the only batter he faced.
Patton, 26, was 4-3 with 14 saves and a 4.08 ERA for Omaha this season. He was selected for the Triple-A All-Star Game on Wednesday night at Durham, N.C. The Royals selected him in the 24th round of the 2011 Draft out of Southern Illinois University-Edwardsville.
Paredes was batting .305 with five homers and 36 RBIs in 65 games for Omaha. He played briefly for Kansas City this year, going 2-for-10 in nine games as a pinch-runner, third baseman and second baseman.
In a Minor League transaction, the Royals dealt left-handed pitcher Ryan Verdugo to the Boston Red Sox for cash. Verdugo was 5-2 with a 4.24 ERA in nine starts for Omaha.
Verdugo was obtained with left-hander Jonathan Sanchez from San Francisco on Nov. 7, 2011 in a trade that sent outfielder Melky Cabrera to the Giants. Vergudo made one appearance for KC, a July 17, 2012, start against Seattle in which he was knocked out in the second inning.