Thornton, 36, has spent eight of his 10 major league seasons in Chicago. He owns a 3.53 ERA and has struck out more than a batter per inning over the course of his MLB career, but his strikeout totals have decreased over the last couple of seasons.
Jacobs, 22, was a 10th-round draft pick by the Red Sox in 2009 and was recently promoted to Double-A. He is hitting .246/.334/.444 with 11 home runs in two minor league stops this season. That's not far off from his career batting line, which is .265/.340/.445.
Boston's starting pitchers have a collective ERA of 3.84, which ranks second in the American League. However, the Red Sox bullpen hasn't matched the success of the team's starters, posting a 4.19 ERA, good for 11th in the AL.
The Red Sox will reportedly receive less than $1 million in cash from the White Sox, according to CBS Sports' Jon Heyman, meaning they'll be responsible for the bulk of the $3.5 million owed to Thornton for the remainder of the season