Kowar was optioned to Triple-A Omaha on Saturday.
Kowar was called up Tuesday and tossed 2.1 scoreless innings while walking two batters and striking out three in Friday's 2-0 loss to the White Sox. With Amir Garrett (personal) being reinstated from the family emergency list Saturday, Kowar will head back to Triple-A. The right-hander could earn another call-up later this summer if a bullpen arm goes down for Kansas City.