Piazza started his rehab at Triple-A Sacramento and went 7-for-17, then played a game with the Class A Stockton Ports on Tuesday night and had a home run in three at-bats.
Piazza is hitting .400 during his stint with a pair of doubles and a pair of RBIs. Piazza hit his home run off Bakersfield's Andrew Walker in the seventh inning of a 15-3 Ports loss.
It was forecasted that Piazza might be out on rehab for 7-10 days, which might land him back in Oakland later this week.
"Yeah, it's possible," A's manager Bob Geren said prior to Wednesday's game. "We have a day off tomorrow, so he'll play there tomorrow night, and then we'll talk about it."
Piazza's bobblehead night at the Coliseum is on Saturday, so the A's slugger could make it back in time to be present when his doll is handed out to thousands of fans.
Geren alluded to the fact that he would likely be activated at some point during the weekend series with Baltimore.
Piazza may have lost a few weeks of game time that could have been spent as a designated hitter after the A's tried to rehab him as a backup catcher, but idea that was scrapped after the All-Star Game.
How ready he would have been, or how ready he is to play every day now still remains a question, but the A's are just happy about the thought of having his bat back in the lineup.
"He's gonna be ready to DH, but I can't predict how many games he'll play right away," Geren said. "But anybody that's a major hitter of his stature is going to help our lineup."
Chavez gets an MRI: A's third baseman Eric Chavez, who missed his third consecutive game on Wednesday afternoon with tightness in his back, underwent an MRI to see if there was any serious damage.
In one of the rare cases where the A's have received good news about an injury, nothing major was discovered.
Geren and the A's are eyeing a weekend return as the A's manager said it would "probably be Saturday." He also added that you might be able to give or take a day with the slight possibility he could be back on Friday, or Sunday.
Dribblers On Wednesday the A's agreed to terms with fifth-round selection Andrew Carignan, a right-handed pitcher out of the University of North Carolina. Carignan had a 1.53 ERA and 18 saves for the Tar Heels this year, leading the NCAA. He struck out 69 batters in 3 innings in earning All-American honors. ... Esteban Loaiza continues his progression towards returning as he threw off the mound again before Wednesday's game. He will continue to throw off the mound every other day until he faces hitters on July 23. He will then throw a side-session on July 25 and face hitters again on July 27. The A's are aiming at having him throw a simulated game or two at the end of the month. ... Huston Street could be back soon, especially if all goes well during his simulated game in Stockton. The closer was scheduled to throw there on Wednesday afternoon. ... Geren planned on giving Nick Swisher a day off, so he gave him Tuesday off to have him ready for Wednesday's day game. Going in Swisher was 7-for-14 with two home runs lifetime off Rangers starter Kevin Millwood.
Up next: A's righty Joe Blanton (8-6, 3.36) will be opposed by Baltimore righty Daniel Cabrera (6-10, 5.16) in the first game of a three-game series on Friday. Game time will be at 7:05 p.m. PT.
Matt Smith is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.