Knehr was recalled from Triple-A El Paso on Tuesday, Kevin Acee of The San Diego Union-Tribune reports.
Knehr joined the big-league club to start during Friday's pseudo-doubleheader, and he returned to El Paso after giving up three runs across four innings. The 24-year-old has a 5.25 ERA, 1.42 WHIP and 15:15 K:BB over 24 major-league innings this season. Craig Stammen (undisclosed) was placed on the injured list in a corresponding move.