Thornton, 36, has been on the disabled list since August 7 (retroactive to August 5) with a right oblique strain. Since being acquired by Boston on July 12, he has gone 0-1 with a 2.16 ERA (2 ER/8.1 IP) in 10 games. Overall this season, Thornton is 0-4 with a 3.47 ERA (14 ER/36.1 IP), 12 walks, and 27 strikeouts in 50 games between the Red Sox and Chicago White Sox.
Villarreal, 26, made one appearance for the Red Sox after being recalled on Monday, walking the only batter he faced. Acquired by Boston from Detroit as part of a three-team, seven-player deal on July 30, he returns to Pawtucket where he has thrown 2.1 scoreless innings over two outings. He also tossed two scoreless outings totaling 2.2 innings for Short-A Lowell on rehab after joining the Red Sox organization.