Janssen has been on the disabled list since the start of the season. He pitched for Class A Dunedin Tuesday, but according to manager John Gibbons he didn't feel better afterward and was told to take a few days off from throwing.
Gibbons said before Thursday's doubleheader at Minnesota he didn't believe the right-hander had a setback. But the manager said Janssen has continued to experience discomfort.
Sergio Santos has handled the ninth-inning role in Janssen's absence.
Shortstop Jose Reyes is expected to rejoin the Blue Jays on Saturday at Cleveland. He strained his left hamstring in his first at-bat this season.