The Padres had to purchase Baxter's contract to add him to their 40-man roster. To make room for Baxter on their 40-man roster, San Diego designated left-handed pitcher Steve Garrison for assignment.
Baxter, 25, can also play first base and will give the Padres another left-handed bat off the bench.
"He's been pretty consistent all year," Padres manager Bud Black said. "He's got an all-around game. He hits with some power and steals some bases."
Baxter, the Padres' fourth-round Draft pick in 2005 out of Vanderbilt, hit a career-high 18 home runs this season with 72 RBIs in 136 games for Portland. He had 30 doubles, 10 triples and 22 stolen bases.
Baxter credits a mechanical fix by manager Terry Kennedy for getting him back on track around the All-Star break. Baxter hit .358 in the second half of the season.
"There was a point where I wasn't hitting really well and TK [Kennedy] pulled me aside and helped fix where I finish, shortening my swing," Baxter said.
Because Baxter wasn't on the 40-man roster and the team -- up until this 10-game losing streak -- had been playing well, he never figured to get a promotion, even after the rosters expanded on Sept. 1.
"I wasn't thinking of where I ranked in the organization or anything, but they had been so successful, you've got to understand that they didn't need to add," Baxter said.