He played in Major League Baseball (MLB) for the Tampa Bay Devil Rays, Atlanta Braves, St. Louis Cardinals, New York Mets, Washington Nationals, and Florida Marlins.

Sosa also played in Nippon Professional Baseball (NPB) for the Chunichi Dragons and Yokohama DeNA BayStars.

Signed by the Colorado Rockies as an amateur free agent in 1995, Sosa spent his first five minor league seasons as an outfielder, but was converted to a pitcher when it was discovered that his arm strength was superior to his batting abilities.

Sosa spent time in the minor league organizations of the Rockies, Seattle Mariners, and Milwaukee Brewers before heading to the Tampa Bay Devil Rays as a Rule 5 draft pick.

Sosa was excited about having the opportunity to start, and responded by going 11-3 as a starter and giving the rotation a major shot in the arm for the season's stretch run.

Still, if not for his performance, it's likely that Atlanta's consecutive string of division championships (which reached 14 before the 2006 season, when the Braves' run finally ended) would have been snapped.

During his strong 2005 season, Sosa earned a reputation for his extraordinary ability to get out of jams he created for himself, as opposing batters hit just .194 with runners in scoring position, and .063 with the bases loaded.

Sosa signed a one-year contract worth $2.2 million with the Braves, and entered the 2006 season back in the rotation.

His struggles, coupled with the Braves' unstable bullpen, prompted manager Bobby Cox to try Sosa in relief.

The pitcher hit his first career home run on April 6, 2006, off Jeff Fassero of the San Francisco Giants.

One month into the season, Orlando Hernández suffered an injury, and Sosa was called up to take his place in the starting rotation while he was recovering.

Sosa's final stat line for his Mets debut was: 61⁄3 IP, 4 hits, 2 Runs, 2 ERs, 2 BBs, 3 Ks.

On May 13, a day after giving up 4 earned runs in one inning against the Washington Nationals, Sosa was designated for assignment by the New York Mets.

On July 25, he signed another minor league contract with the Seattle Mariners, and was assigned to the Triple-A Tacoma Rainiers.

[5] Sosa started as a set-up man but was soon moved to the closer role after Shun Yamaguchi struggled.