Nixon, 33, gives the Diamondbacks some insurance from the left side of the plate as corner infielder Chad Tracy continues to rehabilitate from knee surgery. The team is expected to announce the deal Thursday at its spring training site in Tucson. After completing a physical exam, Nixon will join the Diamondbacks on Saturday.
Nixon is a .275 career hitter with 136 home runs in 11 seasons with Boston and Cleveland. After struggling to stay healthy during the end of his tenure with the Red Sox, he hit .251 with three homers in 307 at-bats for the Indians last season.
Nixon worked out in the outfield and at first base during an open audition at Diamondbacks' camp on Sunday. Seattle, Toronto and the Los Angeles Dodgers also sent scouts to watch him work out.
Arizona's starting outfield is set for 2008 with Eric Byrnes in left field, Chris Young in center and Justin Upton in right, and the Diamondbacks have Mark Reynolds at third base and Conor Jackson at first. But they still aren't sure if Tracy will be ready for Opening Day. After undergoing microfracture surgery on his right knee in September, Tracy suffered a setback in the form of a blood clot. He isn't scheduled to begin light running until this weekend.
The Diamondbacks cut ties earlier this winter with switch-hitter Tony Clark, who hit 17 homers in 221 at-bats in 2007. They expressed a passing interest in veterans Eric Hinske and Mark Sweeney before those two players found jobs elsewhere.
Jerry Crasnick covers Major League Baseball for ESPN.com.