Reddick was forced to exit the club's 5-4 win over the Royals in the bottom of the eighth inning after getting hit by a pitch that bounced off his right shoulder and caromed into the back of his jaw. The A's outfielder was seeing spots after the incident, but all tests indicated he was OK to go Friday.
Pennington, meanwhile, was lost in the bottom of the sixth when he took a foul pitch off his left knee cap. But the A's shortstop was plugged back into a lineup, geared for a third meeting with Seattle righty Felix Hernandez.
Pennington is a career .258 hitter against the 2010 Cy Young Award winner, the best mark of any A's player not named Kurt Suzuki, who has hit Hernandez to the tune of a .313 average with one home run in 32 at-bats.
Elsewhere in the lineup, third baseman Josh Donaldson received his first career start vs. Hernandez. Eric Sogard started the other pair of contests with the right-hander on the mound, but manager Bob Melvin said, "If he's going to be the everyday third baseman, he's going to have to face everybody."
"Certainly he has some power and can run into one," Melvin said of Donaldson. "Against Felix, you don't expect as a team to hit .500 off him, but if you can get one pitch in one spot and take advantage of it, that could be big."
Donaldson collected just one hit in 15 at-bats with seven strikeouts on the last homestand after going 1-for-3 in one game in Tokyo.