Once they put him on the 40-man roster, the A's must pay Inge only a prorated portion of the $480,000 minimum -- or about $412,000 -- of the $5,308,743 he was owed when released by Detroit on Thursday.
Inge hit .100 (2 for 20) with one homer and two RBIs in nine games this season. He turns 35 on May 19 and joins his first new team in his 12th major league season.
"It's a good feeling, but at the same time it's different," Inge said. "Just spending that long in one organization, it's part of my home. But the business side of it is: sometimes you've got to realize when the end is. This is a better fit for me right now, and I'm happy to be here. I was a fan of this team when I was a kid, too. I remember watching Rickey Henderson."
Inge was glad his time out of the game was short.
"It was good. It was three days to get my head straight, to relax a little bit, work out and get ready to come here" he said. "It was perfect timing."
He'll try to fill a void at third, where the A's lost projected starter Scott Sizemore to a season-ending knee injury in the first full-squad workout Feb. 27.
Oakland manager Bob Melvin likes his versatility.
"We've had some difficulty at times this year," Melvin said "We're glad to have him."
Melvin remembers Inge from his days working with Detroit.
"He's a guy I knew coming up as a bench coach," Melvin said. "He could probably play everywhere except pitcher -- and I'm sure he'd try that if we wanted him to. He's a great athlete."
Inge was in the starting lineup, playing third and batting ninth for Monday's game against the Red Sox.
Oakland designated infielder Luke Hughes for assignment Monday to clear roster room.