Toro, who is batting .179 with six homers and 13 RBIs, was injured in Saturday's 6-5 loss when he collided with right fielder Adam Frazier going after a popup in the first inning, hitting the ground after a catch.
The 33-year-old Souza appeared in just six games, going 3-for-19.
To take their places, the team recalled outfielder Taylor Trammell and selected utility player Sam Haggerty from Triple-A Tacoma.
Seattle has lost 19 of its last 25 games, including Sunday's 8-4 loss to the Red Sox in 10 innings, which completed a sweep for Boston.
The Associated Press contributed to this report.