Jeffress, being recalled to the big leagues for the third time this season, has yet to allow an earned run during his time with the Royals, throwing 6.2 innings in eight appearances, allowing six walks and eight hits in that span.
A 24-year-old right-handed pitcher, Jeffress spent a majority of his time with Class AAA Omaha this season. He went 5-4 with an ERA of 4.97 in 37 games before getting optioned to Class AA Northwest Arkansas on Aug. 27. Jeffress was optioned at this point, reports Dutton, because players become available for return with the completion of their minor league team's season, which ended for Northwest Arkansas on Monday.
"It really helps to add another arm," manager Ned Yost said. "Because of the rainout (last Friday) and the double-header (on Saturday), we're using two of our long relievers in (tonight's) game."