Overbay was washing his car on Friday night when he got a call from the D-backs. First baseman Xavier Nady had just suffered a fractured left hand, and the team wanted to know if Overbay was still interested in playing.
Overbay said he was, and the team called back after the game to ink him to a deal.
"It feels good," said Overbay. "I'm excited, I couldn't be in a better position, right now, coming into a playoff atmosphere. And I just want to enjoy the ride."
Overbay, 34, was initially drafted by the D-backs in 1999 and played for them from 2001-03, before being dealt to the Brewers as part of the trade that brought Richie Sexson to Arizona.
Signed as a free agent by the Pirates prior to this season, Overbay was hitting .227 with eight homers and 37 RBIs before his release. With teams having their rosters pretty much set, Overbay was not sure if he would play again.
He spent his time getting acclimated again to Chase Field on Saturday.
"Just trying to get back into baseball shape, into the routine," he said. "You can hit all day at home, but it's still not going to be the same as here."
The D-backs called up top prospect Paul Goldschmidt to play first base two weeks ago. But Overbay provides a left-handed bat, something the club felt it was a little short on.
"He's a veteran guy, has experience," said D-backs manager Kirk Gibson. "Been a pretty good defender. Given what we're up against, he was a very good fit."
To make room on the 40-man roster for Overbay, the D-backs designated right-hander Juan Jaime for assignment. Jaime last pitched in 2009 and underwent Tommy John surgery in April 2010. The D-backs had claimed him on waivers from the Nationals on Nov. 19, 2010.