He's played in just 40 games this year because of an ankle injury he sustained last season and is batting .193 in that span, but "hopefully coming here gives him a little added boost and gives us a little boost as well," assistant general manager David Forst noted.
"We've obviously been looking for a few weeks since before the Deadline to see if there was a chance to get this team some added help, and it worked out with the Diamondbacks that Stephen was available," Forst said. "At times, and certainly before his injury, he was a pretty good offensive player. He's shown that occasionally since he's been back this year."
"We had discussions with them, but Willie [Bloomquist] had the bad back, so the timing wasn't right," Arizona general manager Kevin Towers said. "We would've been very shorthanded. We wanted to get a better idea where we were at. We came close. It didn't happen, but we were able to make it happen through waivers now."
A corresponding 40-man roster move isn't expected until Drew reports Tuesday, with incumbent Cliff Pennington's status up in the air. Pennington's struggles have been well documented this year, with the shortstop batting just .198 with a .549 OPS. Those numbers influenced the A's to look for help near the July 31 Trade Deadline, which quietly passed when the club wasn't able to strike a deal.
That didn't mean Oakland's front-office army was done working, though.
"The middle infield, in general, we've struggled offensively and obviously a change was going to come at some point," said second baseman Jemile Weeks, who is batting .220. "I guess they're trying to make a push, improve in areas they feel they need to improve, and they're trying to head in a certain direction. Obviously they have a vision in their head, and that's' what they're trying to show right now.
"I know him to be a good player in the past. It's news for everybody. It's a surprising thing, and hopefully it's a positive thing for the team. If he comes along and jumps in and fits in and helps us win, we're all for it."
Drew lends the A's something few on the young contending club boast: playoff experience. He enjoyed a remarkable playoff run for Melvin's 2007 National League West Championship team, hitting .387 with two home runs and four RBIs in seven playoff games.
Melvin thought it to be too soon to divulge Drew's expectant role, having not yet announced who the newbie is replacing on the roster, but did say, "He's a good player. He'll be a good fit here."
"Everybody comes in here and fits in," said pitcher Jarrod Parker, a teammate of Drew's in Arizona. "It's a pretty easy going clubhouse. He's been around the game, knows how to play the game and carry himself. He's a good guy."
Drew is in the final year of his guaranteed contract -- with close to $2 million left on his 2012 salary that the A's will pick up -- but has a mutual option for 2013 for $10 million, with a $1.35 million buyout clause.
The hefty option likely means Drew will become a free agent at season's end, though Forst said, "Let's see how the next six weeks go."
"I'm looking forward to going back to an ex-coach. It'll be refreshing and a new start," Drew said. "It's a good feeling to go over there and still be competing."