He alerted team doctors after having trouble using the bathroom, and 20 minutes later, he was on an operating table having his appendix removed.
"I thought it was bubble guts, gas," Fitzpatrick said with a wry laugh.
Fitzpatrick, who said the surgery was his first time under full anesthesia, was at Acrisure Stadium the next day, and a few days after that he was conditioning and practicing with his team.
"Obviously, I was feeling it but I wanted to go out there and support my teammates," Fitzpatrick said about being at the win Sunday.
Fitzpatrick's availability for the Sunday game against the Cincinnati Bengals hasn't been determined, but coach Mike Tomlin was optimistic early in the week.
"Reports regarding Minkah and his inclusion this week are really positive," Tomlin said Tuesday. "I know that he's already been here and run [Tuesday]. I saw him Sunday at the stadium, and Minkah wanted to play on Sunday. Obviously, that wasn't the appropriate thing to do, but that's just the mentality that he brings in. Oftentimes, when you're talking about injury or being unavailable, coming back from lack of availability, your attitude has a lot to do with it and so we're really optimistic about him."
Doctors initially told him it could take anywhere from 10 days to two weeks to fully heal from the emergency surgery, Fitzpatrick told ESPN.
"The worry is when they cut open, they cut through muscle, obviously to get into your stomach," he said. "So you just want to make sure that that's healed properly before you get out there and go."
After not practicing Wednesday, Fitzpatrick was on the field Thursday, and teammate Damontae Kazee didn't notice any difference in the safety coming off surgery.
"It looked like there was no drop-off," Kazee said. "It don't look like he got surgery to me."
Kazee, who signed with the Steelers in free agency and played every snap against the Saints with Fitzpatrick out, said he's not surprised Fitzpatrick is able to bounce back from surgery so quickly.
"That's the dog in him, man," he said. "I always tell Minkah, when I go home, I'll be watching film. I got to steal certain techniques of his that he does at practice. So I think it's pretty cool."
In the Week 1 overtime win against the Bengals, Fitzpatrick returned quarterback Joe Burrow's first pass attempt for a pick-6, and he finished the game with a team-high 14 combined tackles. Even if he can't go Sunday, Fitzpatrick's experience and success against the Bengals will come in handy for whoever fills in for him.
"I think I can help 'em out a lot," Fitzpatrick said. "I've been playing against [the Bengals] for the past four seasons, twice a year, so we're familiar with them. There hasn't been a whole lot of turnover in the receivers and quarterback and offense, so there's a lot I can do to help them."