Atkins, an eight-year veteran, signed a Minor League deal with the club. Wimberly was acquired in a Minor League trade that sent right-handed pitcher Ryan Kelly to Oakland.
In order to make room for Thompson to be added to the 40-man roster, lefty Wil Ledezma was designated for assignment. The Pirates have 10 days to trade, release or outright Ledezma to the Minors, if he clears waivers.
Ledezma has the option of opting for free agency if he clears waivers, though the Pirates are hopeful that he will accept the outright assignment and report to Spring Training, so that he might still compete for a job in the club's bullpen.
Given that Ledezma has already agreed to a Major League contract for 2011, it would seem likely that he'd rather stick with the Pirates then reenter the free-agent market.
Thompson spent almost all of the 2010 season with Washington's Double-A affiliate, where he went 4-13 with a 5.80 ERA in 26 starts. The 23-year-old struck out 95 and walked 53 in 136 2/3 innings. He also made one start in Triple-A.
"Aaron Thompson is a starting pitching prospect and was claimed for his potential," general manager Neal Huntington said. "We have a number of good scouting reports over a handful of years, and those combined with some positive statistical indicators beyond the conventional ERA and won-loss record supported the claim. We believe we can positively impact his growth and development."
By agreeing to terms on a Minor League contract, Atkins is reunited with his former Colorado manager, Clint Hurdle. Atkins played for the Rockies from 2003-09, before signing as a free agent with the Orioles last December.
Atkins appeared in 44 games for Baltimore, but was released in July. He batted .214 with seven doubles, one homer and nine RBIs in 140 at-bats. In his seven seasons with the Rockies, Atkins hit .289 with a .354 on-base percentage. He hit 98 homers and 162 doubles in 773 games.
Of the 781 games the 31-year-old has played in his career, 642 of them have come as a third baseman. Atkins has played 135 games at first, three in the outfield and one at second. The right-handed hitter will be competing to earn a spot on the Pirates' roster as a backup corner infielder.
Wimberly, 27, was a sixth-round pick in the 2005 First-Year Player Draft. Taken by the Rockies, Wimberly played in Colorado's farm system before being dealt to Oakland for Matt Murton in February 2009.
Wimberly has played five different positions in the Minors, though he's been used predominantly as a middle infielder. He swiped 56 bases in 135 games with Triple-A Sacramento last season, giving him 259 career stolen bases in 563 games.
The switch-hitter, who batted .284 in his first season at the Triple-A level, has stolen at least 50 bases in three of his five full Minor League seasons. Though he has not yet appeared in the Majors, Wimberly will likely get a chance to compete for a big league bench spot this spring. The Pirates are looking for someone who can back up Ronny Cedeno and Neil Walker up the middle.
Kelly, a 26th-round pick in 2006, posted a 4.20 ERA in 38 games (one start) with Class A West Virginia last year.