"He told me he was fine," Maddon said. "He tested it. He threw before the game ... but I was still trying to stay away."
Rondon, who is 9-for-9 in save opportunities this season, played catch and said he felt fine after the session.
"I feel way better than yesterday," Rondon said. "I still feel it a little bit, but nothing big."
Rondon, who battled back problems two years ago, felt his back tighten just prior to Wednesday night's 2-1 win over the Dodgers and told the Cubs' athletic trainer that he needed a day.
"I've learned, because I've been through it, that sometimes it's better to lose two days, three days than to lose 10 days, 20 days," Rondon said.
It helped that Jon Lester threw a complete game on Wednesday.
"Yesterday, he did a really good job and they didn't need me," Rondon said of Lester.
Carrie Muskat has covered the Cubs since 1987, and for MLB.com since 2001. She writes a blog, Muskat Ramblings. You can follow her on Twitter @CarrieMuskat and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.