Fresh off a pair of extra-inning games over the weekend that called for arm reinforcements, the A's entered the day with nine relievers, a number that was reduced to eight when lefty Pedro Figueroa was optioned back to Triple-A Sacramento upon Pennington's return.
Oakland's shortstop was originally slated to stay with the River Cats through at least Wednesday.
"We needed an extra position player," manager Bob Melvin said. "It was difficult to go with just three, and especially with Yoenis [Cespedes] a little banged up, that need was there. The bullpen was in a state of flux for obvious reasons, so even though Pedro Figueroa is going down, he really saved us the last couple of days and has contributed here significantly. It's too bad he has to go down, but nine was just too much in the bullpen. Now we're in a little better shape as far as making moves during the course of a game, with an extra position player."
Pennington, a career .231 hitter against Tuesday starter C.J. Wilson, was held out of the lineup with the lefty on the mound, but he confirmed he'll make his first start with the A's since July 19 on Wednesday against Angels right-hander Zack Greinke. He went 5-for-11 in a three-game rehab assignment with Sacramento.
"The elbow feels one thousand times better," said Pennington, who was dealing with tendinitis. "I was just seeing some pitches and getting timing back to get ready to be back here. It's nice to get some hits. It kind of gets you going in the right direction."
The A's hope it continues, having watched Pennington struggle for the majority of the season, as evidenced by his .197 average, including a .152 mark against left-handers, and .259 on-base percentage. With those numbers in mind, Melvin said Adam Rosales will likely still garner some starts against left-handers going forward.