Callaspo will take over at second base for the A's. He's played exclusively at third base this year for the Angels, but he has experience at second, having played 1,773 2/3 innings in 217 games at second in his career.
Callaspo, 30, entered Tuesday night hitting .253/.323/.348 with 13 doubles, five homers, 36 RBI and 32 runs.
Heading into Tuesday, A's second basemen were collectively hitting .254/.320/.340 with 23 doubles and two homers. So the lines are a bit similar, but keep in mind that Jed Lowrie -- now the everyday shortstop -- hit well in 95 plate appearances, skewing things a bit.
Also of note: Callaspo is a switch hitter while lefty Eric Sogard struggles against left-handers (.184 average against heading into Tuesday).
Callaspo is a career .273/.334/.380 hitter.
Green, 25, was 0-for-15 in his debut stint in the majors with the A's this month. The 25 year old was a fairly highly-touted prospect in 2010 and 2011, but his stock has fallen considerably the past few years. Still, he's hitting .325/.379/.500 with 27 doubles and 11 homers in 87 Triple-A games this season -- albeit in the hitter-friendly Pacific Coast League -- so there's some talent in there.