Brandon Allen, acquired in the Brad Ziegler trade from Arizona, will bat sixth and play first base in his Oakland debut.
Allen has split his season among Arizona's Triple-A affiliate, the Reno Aces, the A's Triple-A affiliate, the Sacramento River Cats, and 11 games with the Diamondbacks.
For the Diamondbacks he batted .172 with five hits, three of them home runs, and seven RBI in 11 games.
He batted a combined .299 with 21 homers and 72 RBI in 93 Triple-A games this season.
Manager Bob Melvin described Allen as a "talented guy that's got some power, good athlete, [and a] great first baseman and left field[er]."
"Also, I think, [he] gives us a little dynamic with a left-handed hitter off the bench," continued Melvin. "Potentially he gives us some thump in a pinch-hit role as well, so we're excited to see him."
Melvin later added that Allen "does definitely have some power. They're not all paint scrapers from him, [but] he can hit them back there a ways. Strong kid..."
"He's definitely a guy that can give you some production."
Melvin cautioned that Conor Jackson is still the everyday first baseman, but said Allen will see his fair share of playing time the remainder of the season.
"Conor [Jackson] is, [and] his play in the second half has warranted him to be, the everyday first baseman, but Allen will mix in there," said Melvin. "Like I said, we'll look at him in the outfield some and in a pinch hitting role, and [it's] kind of a work in progress to see how it all shakes out, but we're glad to have him here."
It certainly sounds as if Allen will be given plenty of at-bats in his extended look in the majors prior to the rest of the reinforcements arriving in Oakland when rosters expand on September 1.
The Athletics also recalled right-handed pitcher Bruce Billings from Sacramento and optioned Adam Rosales and Jordan Norberto to Triple-A to make room on the 25-man roster.
Billings was acquired from Colorado in the Mark Ellis trade.
Billings was 6-2 with a 4.67 ERA in 71.1 innings split between Colorado Springs and Sacramento.
Melvin indicated that Adam Rosales's demotion would be another temporary stint in Sacramento.
"He wasn't productive," said Melvin. "He probably fell behind early on. He didn't have a spring training. There's no doubt in my mind he's back September first, if not something happens before that, but I think the extra at-bats will certainly help."