The former football star -- who won season 24 of the show with pro partner Emma Slater -- performed with Cheryl Burke for Movie Night, after news broke that her celebrity partner, Ray Lewis, had to withdraw from the competition due to an injury. Jennings seemed to have no trouble filling in for Lewis, completely nailing Burke's Cha Cha choreography to "Twist and Shout."
Speaking with ET just moments after the performance, Jennings explained just how quickly the dance came together.
"It felt so good to be back!" he raved. "I think we had about a good hour and a half. I got the call Saturday and had to do it, we just fell right into it. It was fun though. I was up for the challenge."
"It's an honor," he added, of stepping in for one of the NFL greats. "Coming from the game of football, growing up and watching how much he changed the game and the dynamic of it... it was very cool to honor him with it."
Knowing from experience just how strenuous competing on the show can be, Jennings said he has his "fingers crossed" that no one else will get hurt this season. (In addition to Lewis, Christie Brinkley had to drop out ahead of premiere night due to an injury she encountered during rehearsals. Her daughter, Sailor Brinkley-Cook, has stepped in for the rest of the season to dance with Val Chmerkovskiy.)
"Listen, the show if full-on," Jennings explained. "It's hard, it's not easy. For myself, even as an athlete, I came into it and I had this big warm-up beforehand. I was doing all this work prior, too, because it's tough."
In case you missed week three of the competition, host Tom Bergeron announced at the top of the show that "an old injury flared up" for Lewis, which is why he wasn't dancing in the opening number. A package then played, showing Lewis at the doctor's -- he tore three tendons and was told he would need to undergo surgery. Lewis revealed that he first tore a tendon in his foot at a game in 2010, and never thought he'd have to deal with this problem again.
"It's an experience I'll never forget," Lewis raved of his brief time on DWTS. "It taught me to dance again."
ET broke the news just hours ahead of showtime -- a source told us that Lewis and Burke were planning to withdraw from the competition due to an injury that the athlete had sustained. Lewis provided even more insight about his injury while chatting with ET on the DWTS press line.
"We went back and forth on the phone at the house at times because I really wanted to push through -- I wanted to figure it out, like, 'Can I go?'" he recalled. "I had been dealing with the pain for a few weeks and once I got the MRI confirmation, reality just got real. Then I called my mom and she said, 'This time you need to follow your heart and not your head.'"
"It was just hard because I love -- I finish things!" he added. "It's a lesson, though right? I learned something from this ... I've lived like this since 2010 with a broken toe and now I can address that and so for me, man, I've been telling people, like, I really want to do this show again."
Burke agreed, telling ET she thinks "we need to do a season of injuries."
"There's been Jewel, Nancy O'Dell," she said. "Like I'm telling you, there's been a lot. People had to bow out."
Hear more in the video below.