"We'll take it slowly in the beginning to make sure everything is in order," Maddon said. "Obviously, he could be a big boon to us if we get this guy back and well."
Isringhausen, who was released by St. Louis after last season, agreed to a minor league deal with the AL champions on Friday.
The right-hander could give Maddon some insurance in the bullpen if closer Troy Percival isn't ready to go after offseason back surgery. Chad Bradford also is expected to be sidelined three to four months after undergoing arthroscopic surgery on his right elbow this month.
"This kind of popped up pretty quick," Isringhausen said about signing with the Rays. "We had talked one time before and we weren't going to do anything, and then it popped up again. With Bradford having surgery, I come in here and add a little more depth. Obviously, I have to pitch to make the team."
Isringhausen has 293 saves and a 3.61 ERA in 13 big league seasons. He had surgery in September to repair a partial tear of his flexor tendon in his elbow.
Isringhausen was 1-5 with 12 saves and a 5.70 ERA in 42 games last season, but Rays executive vice president Andrew Friedman said he thinks the veteran's troubles were due to health issues.
If Isringhausen proves he's healthy this spring, Friedman said he expects him to be with the team on opening day.
"We feel like he's going to fit in great," Friedman said.