Janssen, 32, missed the first six weeks of the season due to a back injury that he originally suffered at the end of spring training.
Toronto's bullpen has struggled during Janssen's absence, entering Sunday with a 4.77 ERA -- the fourth-highest in the majors.
Janssen went 4-1 with a 2.56 ERA and a career-high 34 saves last season, his seventh with the Blue Jays.
Getz was expendable because the Blue Jays intend to use third baseman Brett Lawrie at second against right-handed pitchers so they can keep Juan Francisco in the lineup at third. Lawrie missed his sixth straight game Sunday with a sore right hamstring, but is expected to return Monday.
The Associated Press contributed to this report.