Janssen has been dealing with the injury since the end of Spring Training, and his status for the rest of April appears to be very much in doubt as the tightness continues to linger.
"It's just not right; it's not like it's a lot worse, but he doesn't feel quite comfortable yet to start cutting it loose," said Blue Jays manager John Gibbons. "He's going to take a few days off, from what I understand. ... I don't think he went backwards, but it's not completely out of there to where he feels comfortable."
Right-hander Sergio Santos will continue to receive most of the save opportunities during Janssen's absence. Santos entered play on Thursday with four saves on the season, and left-hander Brett Cecil converted his only opportunity.
The news isn't all bad on the injury front for Toronto, as shortstop Jose Reyes still plans to rejoin the ballclub in Cleveland. Reyes was originally expected to be activated for Friday's game against the Indians, but the Blue Jays will instead wait another day.
Reyes remained at the club's Minor League complex in Florida on Thursday, and he will go through a light workout on Friday before traveling to Cleveland later that night.
"We heard the weather is supposed to be [bad] Friday night, so the plan as of right now is to bring him back hopefully for Saturday's game instead of tomorrow," Gibbons said. "That way, you won't have a night game and then a day game, and you [won't] have to play him two games in 24 hours."
Reyes has been out since he suffered a strained hamstring during his first at-bat of the season. The Blue Jays will likely option either Munenori Kawasaki or Jonathan Diaz to the Minor Leagues upon his return.
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.